FFmpeg by Example
(ffmpegbyexample.com)878 points by piyushsthr 4 days ago
878 points by piyushsthr 4 days ago
I use ffmpeg multiple times a week thanks to LLMs. It's my top use-case for my "llm cmd" tool:
uv tool install llm
llm install llm-cmd
llm cmd use ffmpeg to extract audio from myfile.mov and save that as mp3
I tried this (though with a different tool called aichat) for extremely simple stuff like just "convert this mov to mp4" and it generated overly complex commands that failed due to missing libraries. When I removed the "crap" from the commands, they worked.
So much like code assistance, they still need a fair amount of baby sitting. A good boost for experienced operators but might suck for beginners.
Plus you need to know the format of your source file to design the command correctly. How many audio tracks, is the first video track a thumbnail or the video, are the subtitles tracks forced, etc.
And in some situations ffmpeg has some warts you have to go around. Like they introduced recently a moronic change of behaviour where the first sub tracks becomes forced/default irrespective of the original forced/default flag of the source. You need to add "-default_mode infer_no_subs" to counter that.
My feelings exactly, but I think that's OK!
It's another tool and one that might actually improve with time. I don't see GNU's man pages getting any better spontaneously.
Whoa, what if they started to use AI to auto-generate man pages...
Reading this feels like seing a guy getting his first car in 1920 and complaining he still has to drive it himself.
My experience exactly.
I no longer check with these AI tools after a number of attempts. Unrelated, a friend thought there was a NFL football game last Saturday at noon. Checking with Google's Gemini, it said "no", but there was one between two teams whose season had ended two weeks before at 1:00 Eastern Time and 2:00 Central. (The times are backwards.)
> "convert this mov to mp4"
Did any of the commands look like the ones in the left window:
https://beta.gitsense.com/?chats=12850fe4-ffb1-4618-9215-c13...
The left window contains a summary of all the LLMs asked, including all commands. The right window contains the individual LLM responses.
I asked about gotchas with missing libraries as well, and Sonnet 3.5 said there were. Were these the same libraries that were missing for you?
what exactly do you want the llm to do here? if the ask was so unambiguous and simple that it could be reliably generated, then the interface wouldn't be so complicated to use in the first place! LLMs are not in any way best suited for one-shot prompt => perfect output, and expectations to that effect are extremely unreasonable. the reason why LLMs are still hard for beginners to use is because the software is hard to use correctly. as with LLM output goes life itself: the results you get from using a tool can only ever be as good as the (mental) model used to choose that tool & the inputs to begin with. if all the information required to generate the output were contained by the initial prompt, then there would be absolutely no need to use the LLM at all in the first place.
Hate to be that guy, but which LLM was doing the generation? GPT-4 Turbo / Claude 3.x have not really let me down in generating ffmpeg commands - especially for basic requests - with most of their failures resulting from domain-specific vagaries that an expert would need to weigh in on m
A while back I simply wrote my own bash function for this called `please`
as in
bash> please "use ffmpeg to extract audio from myfile.mov and save it as mp3"
Here is the whole thing, with its two dependent functions, so that people stop writing their own versions of this lol. All it needs is an OPENAI_API_KEY, feel free to modify for other LLMs
EDIT: Moved to a gist: https://gist.github.com/pmarreck/9ce17f7996347dd532f3e20a2a3...
Suggestions welcome- for example I want to add a feature that either just copies it (for further modification) or prepopulates the command line with it somehow (possibly for further modification, or even for skipping the approval step)
please is such an appropriate name. Will rename my ChatGPT alias to please.
>This will then be displayed in your terminal ready for you to edit it, or hit <enter> to execute the prompt. If the command doesnt't look right, hit Ctrl+C to cancel.
I appreciate the UI choice here. I have yet to do anything with AI (consciously and deliberately, anyway) but this sort of thing is exactly what I imagine as a proper use case.
Just like all other code. There will be user-respecting open source code and tools, and there's user-disrespecting profitable closed code that makes too many decisions for you.
Hypertalk <https://en.wikipedia.org/wiki/HyperTalk> lives.
I think I’m finally sold on actually attempting to add some LLM to my toolbelt.
As a helper and not a replacement, this sounds grand. Like the most epic autocomplete. Because I hate how much time I waste trying to figure out the command line incantation when I already know precisely what I want to do. It’s the weakest part of the command line experience.
But possibly the most rewarding. The struggle is its own reward that pays off later many times over.
For the longest time I had ffmpeg in the same bucket as regex: "God I really need to learn this but I'm going to hate it so much." Then ChatGPT came along and solved both problems!
Interesting. Being able to use regexps for text processing through my career has probably saved me a few thousand hours of programming one-off solutions so far. It is one of those skills that really pays off to learn proper.
And speaking of ffmpeg, or tooling in general, I tend to make notes. After a while you end up with a pretty decent curated reference.
I use regexes a lot. The main thing that always trips me up is dealing with escaping, because different tools I use – vim, sed, rg, and so on – sometimes have different meanings for when to escape or not.
In one tool you’ll use + to match one or more times, and \+ to mean literal plus sign.
In another tool you’ll use \+ to match one or more time, and + to mean literal plus sign.
In one tool you’ll use ( and ) to create a match group, and \( and \) to mean literal open and close parentheses.
In another tool you’ll use \( and \) to create a match group, and ( and ) to mean literal open and close parentheses.
This is basically the only problem I have when writing regexes, for the kinds of regexes I write.
Also, one thing that’s not a problem per se but something that leads me to write my regexes with more characters than strictly necessary is that I rarely use shorthand for groups of characters. For example the tool might have a shorthand for digit but I always write [0-9] when I need to match a digit. Also probably because the shorthand might or might not be different for different tools.
Regexes are also known to be “write once read never”, in that writing a regex is relatively easy, but revisiting a semi-complicated regex you or someone else wrote in the past takes a little bit of extra effort to figure out what it’s matching and what edits one should make to it. In this case, tools like https://regex101.com/ or https://www.debuggex.com/ help a lot.
No one doubts the power or utility of regexes or ffmpeg, but they are both complicated beasts that really take a lot of skill.
They're both tools where if they're part of your daily workflow you'll get immense value out of learning them thoroughly. If instead you need a regex once or twice a week, the benefit is not greater than the cost of learning to do it myself. I have a hundred other equally complicated things to learn and remember, half the job of the computer is to know things I can't put in my brain. If it can do the regex for me, I suddenly get 70% of the value at no cost.
Regex is not a tool I need often enough to justify the hours and brain space. But it is still an indespensible tool. So when I need a regex, I either ask a human wizard I know, or now I ask my computer directly.
Not sure about ffmpeg, but you should definitely try memorising regexp. Casual Search&replace that becomes possible is worth it.
in 15 years it never sticks and by the time i need it again i've forgotten it! :D
Gotta be honest, years of configuring automod on Reddit have honed me into a regex God.
... Then ChatGPT came along and I had 3 problems! https://regex.info/blog/2006-09-15/247
My rule for using LLMs is that anything that's one off is okay. Anything that's more permanent and committed to a repo needs a human review. I strongly suggest you have an understanding of the basics (at least the box model) so that you are competent at reviewing CSS code before using LLM for that.
Same here, it's one of these things where AI has taken over completely and I'm just a broker that copy-pastes error traces.
In addition to the many others mentioned, here's a script I just threw together that simplifies a lot of these chained commands - llmpeg: https://github.com/jjcm/llmpeg
If you have ffmpeg installed and an OpenAI env api key set, it should work out of the box.
Demo: https://image.non.io/1c7a92ef-0917-49ef-9460-6298c7a9116c.we...
My experience got even better once I learned how complex filters worked.
learning how to use splits to do multiple things all in one command is a god send. the savings of only needed to read the source and convert to baseband video once is a great savings.
i started with avisynth, and it took time for my brain to switch to ffmpeg. i don't know how i could function without ffmpeg at this point
Truly, a net positive to my life. Just a few days ago I asked my AI buddy (Claude) to create a zsh script to organize my downloads folder according to the Johnny Decimal system. I’ve since modified it to move the files to a JD setup on my desktop.
The sense of elation I get when I wonder aloud to my digital friend and they generate what I thought was too much to expect. Well worth the subscription.
I ended up creating my own tool to generate ffmpeg commands https://newbeelearn.com/tools/videoeditor/
I think you're onto something. I've had hit or miss experiences with code from LLMs but it definitely makes the searching part different.
I had a problem I'd been thinking about for some time and I thought "Ill have some LLM give me an answer" and it did - it was wrong and didn't work but it got me to thinking about the problem in a slightly different way and my quacks after that got me an exact solution to this problem.
So I'm willing to give the AI more than partial credit.
Basic syntax for re-encoding a video file did take me some time to memorize, but isn't in fact too hard:
ffmpeg <Input file(s)> <Codec(s)> <MAPping of streams> <Video Filters> output_file
ffmpeg -i file1.mp4 -i file2.mkv
- codec: -c:x where x is the type of codec (v: video, a: audio or s:subtitles), followed by its name, like so:
-c:v libx265
- mapping of streams: -map <input_file>:<stream_type>:<order>, like so:
-map 0:v:0 -map 1:a:1 -map 1:a:0 -map 1:s:4
The position of the stream in the output file is determined by the position of the map command in the command line, so for example in the command above we are inverting the position of the audio streams (taken from 'file2.mkv'), as audio stream 1 will be in first position in the output file, and audio stream 0 (the first in the second input file) will be in second position in the output file.
This map thing is for me the most counter-intuitive because it's unusual for a CLI to be order-dependent. But, well, it is.
- video filters: -vf
Video filters can be extremely complex and I don't pretend to know how to use them by heart. But one simple video filter that I use often is 'scale', for resizing a video:
-vf scale=<width>:<height>
-vf scale=320:-1
And that's about it! ffmpeg options are immense, but this gets me through 90% of my video encoding needs, without looking at a manual or ask an LLM. (The only other options I use often are -ss and -t for start time and duration, to time-crop a video.)
> This doesn't always work because the computed value should be an even integer; if it's not, ffmpeg will raise an error and tell you why; then you can replace the -1 with the nearest even integer (I wonder why it can't do that by itself, but apparently, it can't).
It's not about integer, but some of the sizes need to be even. You can use `-vf scale=320:-2` to ensure that.
It's hard for a number to be even without first being an integer, no? ;-)
But thanks for '-2', didn't know about that! It's the exact default option I needed! Will be using that always from now on.
https://stackoverflow.com/questions/71092347/ffmeg-option-sc...
> then you can replace the -1 with the nearest even integer (I wonder why it can't do that by itself, but apparently, it can't).
Likely because the aspect ratio will no longer be the same. There will either be lost information (cropping), compression/stretching, or black bars, none of which should be default behaviour. Hence, the warning.
I would like to throw in a tool that I built into the ring: gencmd - https://gencmd.com/. There is a web version and also a CLI version.
If the CLI is installed, you can do: gencmd -c ffmpeg extract first 1 minute of video
Or you can just search for the same in the browser page.
ffmpeg and jq are 2 commands I've about given up trying to "use" with any facility and am more than happy to pawn that off to one of the Gippity's; chat, claude, etc.
This reminds me I need to publish my write up on how I've been converting digitized home video tapes into clips using scene detection, but in case anyone is googling for it, here's a gist I landed on that does a good job of it [0] but sometimes it's fooled by e.g. camera flashes or camera shake so I need to give it a start and end file and have ffmpeg concatenate them back together [1]
Weird thing is I got better performance without "-c:v h264_videotoolbox" on latest Mac update, maybe some performance regression in Sequoia? I don't know. The equivalent flag for my windows machine with Nvidia GPU is "-c:v h264_nvenc" . I wonder why ffmpeg doesn't just auto detect this? I get about 8x performance boost from this. Probably the one time I actually earned my salary at work was when we were about to pay out the nose for more cloud servers with GPU to process video when I noticed the version of ffmpeg that came installed on the machines was compiled without GPU acceleration !
[0] https://gist.githubusercontent.com/nielsbom/c86c504fa5fd61ae...
[1] https://gist.githubusercontent.com/jazzyjackson/bf9282df0a40...
> Probably the one time I actually earned my salary at work was when we were about to pay out the nose for more cloud servers with GPU to process video when I noticed the version of ffmpeg that came installed on the machines was compiled without GPU acceleration !
Issue with cloud CPU's is that they don't come with any of the consumer grade CPU built-in hardware video encoders so you'll have to go with the GPU machines that cost so much more. To be honest I haven't tried using HW accel in the cloud to have a proper price comparison, are you saying you did it and it was worth it?
Are the hardware encoders even good? I thought that unless you need something realtime, it's always better to spend the cpu cycles on a better encode with th software encoder. Or have things changed ?
They still suck compared to software encoders. This is true for both H.264 and H.265 on AMD, Nvidia, and Intel GPUs. They’re “good enough” for live streaming, or for things like Plex transcoding, or where you care only about encoding speed and have a large bandwidth budget. They’re better than they used to be, but not worth using for anything you really care about.
That's my experience too. I transcode a lot of video for a personal project and hardware acceleration isn't much faster. I figure that's because on CPU I can max out my 12 cores.
The file size is also problematic I've had hardware encodes twice as large as the same video encoded with CPU.
We were a quick and dirty R&D team that had to do a lot of video processing quickly, we were not very cost sensitive and didn’t have anything other than AWS to work with, so I can’t speak to whether it was worth it :)
In your snippets, you don't appear to be deinterlacing. If your pre-digitized clips are already deinterlaced, that's fine, but if they're not, you're encoding interlaced material as progressive, and mangling the quality. Try adding a bwdif filter so that your 30i content gets encoded as 60p (which will look more like the original videotapes).
Then can you merge all the clips starting when motion starts and see hundreds of planes fly across at once?
Interesting. Yes, I assume that's possible although I'm not sure how you handle the background- I guess you find an empty frame, and subtract that from every image with a plane.
One of the advantages of working with image data is that movies are really just 3d data and as long as all the movies you work with are the same size, if you have enough ram, or use dask, you could basically do this in a couple lines of numpy.
You could do an add operation if the background is dark enough, or yeah, take a local sample of the background to subtract from each clip, and choose a specific background...
> I wonder why ffmpeg doesn't just auto detect this?
Hardware encoding is often less configurable and involves greater trade-offs than using sophisticated software codecs, and don't produce exactly equivalent results even with equivalent parameters. On top of that, systems often have multiple hardware APIs to choose from that often different features.
FFMpeg is a complex command-line tool intended for users who are willing to learn its intricacies, so I'm not sure it makes sense for it to set defaults based on assumptions.
-c:v h264_nvenc
But in my limited experiments a while back, I found the output quality to be slightly worse than with libx264. I don't know if there's a way around it, but I'm not the only one who had that experience.
IIRC they have improved the hardware encoder over the generations of cards, but yes NVENC has worse quality than libx264. NVENC is really meant for running the compression in real-time with minimal performance impact to the system. Basically for recording/streaming games.
Fascinating, it didn't occur to me quality could take a hit, I thought the flag merely meant "perform h264 encoding over here"
Edit: relevant docs from ffmpeg, they back up your perception, and now I'm left to wonder how much I want to learn about profiles in order to cut up these videos. I suppose I'll run an overnight job to reencode them from Avi to h264 at high quality, and make sure the scene detect script is only doing copys, not reencoding, since that's the part I'm doing interactively, there's no real reason I should be sitting at the computer while its transcoding.
Hardware encoders typically generate output of significantly lower quality than good software encoders like x264, but are generally faster and do not use much CPU resource. (That is, they require a higher bitrate to make output with the same perceptual quality, or they make output with a lower perceptual quality at the same bitrate.)
I've gotten pretty good at various bits of ffmpeg over time. Its CLI has a certain logic to it... it's order dependent (not all unix CLIs are).
Lately, I've been playing around with more esoteric functionality. For example, storing raw video straight off a video camera on a fairly slow machine. I built a microscope and it reads frames off the camera at 120FPS in raw video format (YUYV 1280x720) which is voluminous if you save it directly to disk (gigs per minute). Disks are cheap but that seemed wasteful, so I was curious about various close-to-lossless techniques to store the exact images, but compressed quickly. I've noticed that RGB24 conversion in ffmpeg is extremely slow, so instead after playing around with the command line I ended up with:
ffmpeg -f rawvideo -pix_fmt yuyv422 -s 1280x720 -i test.raw -vcodec libx264 -pix_fmt yuv420p movie.mp4 -crf 13 -y
Because I hate command lines, I ended up using ffmpeg-python which composes the command line from this:
self.process = (
ffmpeg.
input(
"pipe:",
format="rawvideo",
pix_fmt="yuyv422",
s="{}x{}".format(1280, 720),
threads=8
)
.output(
fname, pix_fmt="yuv422p", vcodec="libx264", crf=13
)
.overwrite_output()
.global_args("-threads", "8")
.run_async(pipe_stdin=True)
)
I'm still looking for better/faster lossless YUV encoding.
>Its CLI has a certain logic to it... it's order dependent (not all unix CLIs are).
Which is appropriate. A Unix pipeline is dependent on the order of the components, and complex FFMpeg invocations entail doing something analogous.
>I ended up using ffmpeg-python which composes the command line from this
A lot of people like this aesthetic, but doing "fluent" interfaces like this is often considered un-Pythonic. (My understanding is that ffmpeg-python is designed to mirror the command-line order closely.) The preference (reinforced by the design of the standard library and built-in types) is to have strong https://en.wikipedia.org/wiki/Command%E2%80%93query_separati... . By this principle, it would look something more like
ffmpeg(global_args=..., overwrite_output=True).process_async(piped_input(...), output(...))
To be honest what I really wanted is more like a programming API or config file than attempting to express complex pipelines and filters in a single command line.
As for what's unpythonic: don't care. My applications has code horrors that even Senior Fellows cannot unsee.
Similar, arguably simpler, Python library that provides an interface to FFmpeg command line is ffmpy [0], of which I am the author.
> I'm still looking for better/faster lossless YUV encoding.
Look no further: https://trac.ffmpeg.org/wiki/Encode/FFV1
>> I'm still looking for better/faster lossless YUV encoding.
> I wasn't able to produce results that were convincingly better than libx264
With "-qp 0"? Otherwise, it's not a valid comparison... "-crf 13" is nowhere near lossless (though it might appear so visually).
FFV1 is much better than H264 at lossless compression in my experience. Here's a random sample of a ten second 4K input I had handy (5.5G uncompressed):
h264-ultrafast 1.951s 850M
h264-veryslow 46.528s 715M
ffv1 8.883s 637M
I am here to sell you on one word: ramdisks.
If you are doing processing with intermediate steps you do not want to keep? Ramdisks. Oh yeah. Oh yeah.
This seems to be very forgotten tech. First time I used that was to load NetHack to ram instead of the slow diskette on my Atari. Now I still use it as webcache for work to not bother the database with so many requests.
When I set up the server, the ramdisk didn't have a way of shrinking when space wasn't needed so had to make sure it doesn't eat up all memory when growing unlimited. I bet it's smarter nowadays.
Ok, but it was very forgotten in my circles when I suggested we use a ramdisk. Ours was at /dev/shm/ I think. Noone had heard of ramdisks and sounded a bit skeptical but the server is still running and no problems with sluggish pages any more.
Ramdisks are so very handy now when you can have much more than 512 kB ram... :-)
Slow ffmpeg pipelines are typically cpu-bound rather than io-bound.
e.g. When doing a simple copy, progress status messages upgrade to scientific notation.
I thought this was going to be a website managed by an experienced user of FFmpeg sharing from their collection of accumulated knowledge, but then was immediately disappointed on the first example I clicked on.
https://www.ffmpegbyexample.com/examples/l1bilxyl/get_the_du...
Don’t call two extra tools to do string processing, that is insane. FFprobe is perfectly capable of giving you just the duration (or whatever) on its own:
ffprobe -loglevel quiet -output_format csv=p=0 -show_entries format=duration video.mp4
Nice! This reminds me of my own ffmpeg cheatsheet; I would imagine that everyone who uses ffmpeg frequently has a similar set of notes
FFmpeg is one of those tools I need to use so infrequently that he exact syntax never seems to stick. I've resorted to using an LLM to give me the command line I need. The only other tool that I ever had trouble with was 1990s-era MegaCLI from LSI Logic, also something I barely used from one year to the next (but one where you really need to get it right under pressure).
I've been using FFMPEG for 15+ years, and still can't remember almost any commands. LLMs have been amazing for using FFMPEG though. ChatGPT and Claude do wonders with "give me an ffmpeg command that will remux a video into mkv, include subtitle.srt in the file, and I only want it between 0:00:05 and 0:01:00." It produced this in case you were wondering: `ffmpeg -i input.mp4 -i subtitle.srt -ss 00:00:05 -to 00:01:00 -map 0 -map 1 -c copy -c:s mov_text output.mkv`
I wonder how small of an LLM you could develop if you only wanted to target creating ffmpeg commands. Perhaps it could be small enough to be hosted on a static webpage where it is run locally?
Perhaps small enough to include in ffmpeg itself so you can just write commands `ffmpeg do this thing I want`.
Now I say this, it seems like there should already be a shell that is also an LLM where you can mix bits of commands you vaguely remember and natural language a bit like Del Boy speaking French...
That would be an amazingly useful feature of ffmpeg, and considering how large its dependencies are (390MB of packages for `apt install ffmpeg` on a fresh Raspberry Pi OS install), it would be reasonable to have an optional model package.
https://github.com/warpdotdev/Warp
https://www.warp.dev/blog/how-warp-works
Warp terminal – no more login required (49 days ago) https://news.ycombinator.com/item?id=42247583
Show HN Warp.dev (3 years ago) https://news.ycombinator.com/item?id=30921231
Show HN llmterm https://news.ycombinator.com/item?id=42498901 https://github.com/timschmidt/llmterm
I was kind of curious about that one too. It is encoding the SRT into the MP4/MOV subtitle format. I use it all the time when muxing subs into MP4s, but I haven't seen what happens with an MKV like that. It is very well supported in MP4s.
I've just maintained my own note doc, going on 15 years now, of my most commonly used syntax. When that fails, I grep my bash history.
Same. The only thing that sticks is converting from format X to .mp4. Everything else I need to look up every single time.
Relevant XKCD https://xkcd.com/1168/
Don't forget that Gstreamer exists and its command line and documentation make a little bit more sense than ffmpeg because GStreamer is pipeline based and the composition is a little bit more sane. I stopped using ffmpeg entirely and only use GStreamer for intense video work.
Gstreamer can give you more control and has friendlier API's if you're gonna make a pipeline programatically but for one off stuff ffmpeg seems much friendlier to me. For example it has sane x264 defaults while with gst-launch you have to really know what you're doing to get quality x264 encoding
I wish there was some sort of local gui / tool to drag and drop nodes, connect them together, type-check the graph if possible, and it would only show the ffmpeg command to run which you could paste. Anyone know or anything?
You're right, but gstreamer is a little bit more sane for many use cases. Maybe ffmpeg is more advanced; I am not sure. I find the pieces fit together better with gstreamer.
Not sure about the vulns but I am actively discussing things with the devs on their Matrix
Here is the GitHub repo for a ffmpeg book which may be a nice supplement to this site:
ffmpeg has always felt like a gui application crammed into tui format. I've had the displeasure of using the C api a few times, while it's straight forward in many respects, it makes invalid states extremely easy to represent. I would love a realtime AV1 encoding framework that "just works".
> ffmpeg has always felt like a gui application crammed into tui format.
It’s one of the only tools where I reach for a GUI equivalent (Handbrake) by default, unless I’m doing batch processing. There are a few pure ffmpeg GUIs out there as well. There’s just something about working with video that CLI doesn’t work right with my brain for.
I can vouch for GStreamer as an API. I was using the Rust bindings so not super familiar with the C API but it looks good. GObject makes some things verbose but once you understand it you can interact with every object in the API consistently. There is a ton of necessary complexity (video is hard) but it’s really well designed and pretty well implemented and documented.
If you have a pretty normal use case the Bins (decodebin, transcodebin, playbin) make that pretty easy. If you have a more complex use case the flexibility of the design makes it possible.
ffmpeg API is somewhat clunky but it works fine. I dread working with gstreamer, sea of leaky abstractions, inexplicable workarounds and mysterious bugs.
I like this insight, but TUI is something graphical while ffmpeg is just CLI.
It would be cool to see if a TUI tool existed. Something like https://github.com/Twinklebear/fbed but more feature complete.
One thing on Linux systems I like to do is build ffmpeg statically.. as distro versions are sometimes too old or don't include modules I prefer.. this containerized version has done wonders for me https://github.com/wader/static-ffmpeg
The AMIA has a resource for this as well at https://amiaopensource.github.io/ffmprovisr/
It's not a great name and not very discoverable, but there's a lot of very useful ffmpeg-by-example snippets there with illustrated results, and an explanation of what each option in each example does.
I love using FFMpeg via Wasm for ... senseless ... mini projects i.e.: https://video-2-sprites.franzai.com/ Video 2 Sprites Converter - totally over-engineered
Love the bouncing progress bar. Also nice ffmpeg wasm only 11MB
I love "X by Example" sites! But if you don't work with a tool like ffmpeg imagemagick day in and out, there's no way you'll remember their unintuitive syntax or will want to spend the time to get your one-time job done. I'd still probably not use this site to scan a dozen of examples and try to put together the pieces of the puzzle; instead, I'd probably just use an LLM who already scanned the entire web corpus and can probably get me to a solution faster, right? At that point, I wonder what folks get out of this site?
I was excited to see this as just last night I was using FFmpeg to combine digital (legally owned) movies with multiple parts into a single MKV file. It worked great, the one thing (and this is undoubtedly just a knowledge problem on my part), is I could not get it to copy/include subtitles from both parts. I have a feeling I might need to extract the subtitle files and combine them and then re-include the combined version, but was hoping there would be a solution in this site for doing something like that. Unfortunately, I didn't even see the combine as one of the examples.
For reference:
One-liner:
> ffmpeg -loglevel info -f concat -safe 0 -i <(for f in *.mkv; do echo "file '$(pwd)/$f"; done) -c copy output.mkv
Or the method I ended up using, create a files.txt file with each file listed[0]
> ffmpeg -f concat -safe 0 -i files.txt -c copy output.mkv
files.txt
> file 'file 1.mkv' > file 'file 2.mkv' > # list any additional files
One thing I have never been able to do reliably is get ffmpeg to split a file based on a fixed size - e.g. break this video into 100MB chunks.
The closest I seem to be able to get is to divide the file size by the file length, add some wiggle room and then split it based on time. Any pointers appreciated.
also worthwhile consulting this resource: https://www.youtube.com/watch?v=9kaIXkImCAM
I just use LLMs to help me with ffmpeg (and many other similarly complex tools) commands: https://github.com/dheera/scripts/blob/master/helpme
$ helpme ffmpeg capture video from /dev/video0 every 1 second and write to .jpg files like img00000.jpg, img00001.jpg, ...
$ helpme ffmpeg assemble all the .jpg files into an .mp4 timelapse video at 8fps
$ helpme ffmpeg recompress myvideo.mp4 for HTML5-friendly use and save the result as myvideo_out.webm
"Print a text file to STDOUT using ffmpeg" ffmpeg -v quiet -f data -i input.txt -map 0:0 -c text -f data - I tried this in a directory with input.txt with some random text Nothing.
So changed the verbosity to trace ffmpeg -v trace -f data -i input.txt -map 0:0 -c text -f data -
---snip-- [dost#0:0 @ 0x625775f0ba80] Encoder 'text' specified, but only '-codec copy' supported for data streams [dost#0:0 @ 0x625775f0ba80] Error selecting an encoder Error opening output file -. Error opening output files: Function not implemented [AVIOContext @ 0x625775f09cc0] Statistics: 10 bytes read, 0 seeks
I was expecting text to be written to stdout? What did I miss?
It's not working for me either, on FFmpeg 7.0.2. I suspect something has changed in FFmpeg since that command was shared on the Reddit post mentioned on the website. That was a few years ago.
However, from the same Reddit thread, this works:
ffmpeg -v quiet -f data -i input.txt -map 0 -f data pipe:1
EDIT: just verified the `-c text` approach works on FFmpeg major versions 4 and 5. From FFmpeg 6 onwards, it's broken. The `pipe:1` method works from FFmpeg 5 onwards, so the site should probably be updated to use that instead (also, FFmpeg 5.1 is an LTS release).
When I read that, it resembles very much the format of responses from copilot.microsoft.com
especially: point 4 is the final giveaway!
Ha, very literal answer, why not use cat to print the file, is that a bit of sarcasm creeping into the LLM's?
In fact, that LLMs are typically steered away from sarcasm or irony (i guess via system prompts stressing on formalism), makes it easier to identify their output. Its output is so formal, taking the question very seriously though it is obviously just an exercise, that it sounds ironical.
I'm grateful for sites like this and these days LLMs too. ffmpeg is awesome, but I can never rememeber the right incantation. The sites/tools get me the right ffmpeg answer, but I still needed to remember the answer next time (or look things up again). Now I save them as reusable commands: https://lmno.lol/alvaro/how-i-batch-apply-and-save-one-liner...
The great ffmpeg!, Even though you can generate commands using llm its still tedious to adjust things visually on cli so I ended up creating my own tool to generate ffmpeg commands.
Ya know, it's websites like this that make me want to see a "best of HNN" list, so it can be easily found when I'm using ffmpeg and saying "geez, there was some cool ffmpeg site, but where the heck is it?...."
Can we have a best of HNN and put it on there, or vote on it, or whatever?
You can "favorite" individual comments or entire submitted threads and revist them via your ( https://news.ycombinator.com/user?id=Over2Chars ) user page favorite links.
Which indeed you have: https://news.ycombinator.com/favorites?id=Over2Chars
There are a number of HN lists: https://news.ycombinator.com/lists
"Best": https://news.ycombinator.com/best is highest voted recent links.
Nice! I am a HNN newb.
I finally found that six point font "favorite" that appears only once and at the top of the comment section for a topic.
You guys don't make it easy.
I think at this point docs should start to be written not for humans but for LLMs, i.e. package all of it up with the --help into one giant txt file for easy attachment to an LLM when asking the question you'd like. Imo it's a relatively good fit to the current capability.
Somebody please pay people to create sites like this so LLMs can train on them and I never have to spend time thinking about arcane FFMPEG commands ever again. I remember losing whole days in the before times trying to figure out how to make FFMPEG do some highly specific set of things.
ffmpeg is so goated, I used it to merge video/audio from a mic on a camera I made ha
there was one time I didn't use pyaudio correctly so I was using this process where ffmpeg can stitch multiple audio files together into one passed in as an array cli argument, crazy
hey everyone, thanks for the "hunt".
Currently looking for an FFmpeg related job https://gariany.com/about
I was pretty happy because I was able to actually do something in ffmpeg recently. It is this amazingly powerfully tool, but every time I try to use it I get scared off by the inscrutable syntax. But this time as the mental miasma that usually kills my ffmpeg attempts was setting in I noticed something in the filter docs, a single throw away line about including files and the formatting of filters
Anyway long story short, instead of the usual terrifying inline ffmpeg filter tangle. the filter can be structured however you want and you can include it from a dedicated file. It sounds petty, but I really think it was the thing that finally let me "crack" ffmpeg
The secret sauce is the "/", "-/filter_complex file_name" will include the file as the filter.
As I am pretty happy with it I am going to inflect it on everyone here.
In motion_detect.filter
[0:v]
split
[motion]
[original];
[motion]
scale=
w=iw/4:
h=-1,
format=
gbrp,
tmix=
frames=2
[camera];
[1:v]
[camera]
blend=
all_mode=darken,
tblend=
all_mode=difference,
boxblur=
lr=20,
maskfun=
low=3:
high=3,
negate,
blackframe=
amount=1,
nullsink;
[original]
null
ffmpeg -nostats -an -i ip_camera -i zone_mask.png -/filter_complex motion_display.filter -f mpegts udp://127.0.0.1:8888
explanation:
"[]" are named inputs and outputs
"," are pipes
";" ends a pipeline
take input 0 split it into two streams "motion" and "original". the motion stream gets scaled down, converted to gbrp(later blends were not working on yuv data) then temporally mixed with the previous two frames(remove high frequency motion), and sent to stream "camera". Take the zone mask image provided as input 1 and the "camera" stream, mask the camera stream, find the difference with the previous frame to bring out motion, blur to expand the motion pixels and then mask to black/white, invert the image for correct blackframe analyses which will print messages on stdout when too many motion pixels are present. The "original" stream get sent to the output for capture.
One odd thing is the mpegts, I tried a few more modern formats but none "stream" as well as mpegts. I will have to investigate further.
I could, and probably should have, used opencv to do the same. But I wanted to see if ffmpeg could do it.
No one seems to be talking about the website itself.
While as a concept, I absolutely love "X by Example" websites, this one seems to make some strange decisions. First, the top highlighted example is just an overly complicated `cat`. I understand that it's meant to show the versatility of the tool, but it's basically useless.
Then below, there's 3 pages of commands, 10 per page. No ordering whatsoever in terms of usefulness. There looks like there's an upvote but it's actually just a bullet decoration.
There's also a big "try online" button for a feature that's not actually implemented.
All in all, this is a pretty disappointing website that I don't think anyone in this thread will actually use, even though everyone seems to be "praising" it.
Creator of the site here, thanks for your comment.
The build system randomize an example to showcase on the homepage, I actually find it funny that its different example every time.
Regarding the upvote system. This is a static documentation website. I have created a crazy unique solution to have upvotes working but the website had literally zero traffic in years, so I guess that wasn't the most important feature to focus on.
Sorry to disappoint, I'm doing it completely voluntary - happy to get any help here: https://github.com/eladg/ffmpeg-by-example
I use Ffmpeg. I have zero interest in cloud based Ffmpeg.
Maybe if it was really cheap and the servers could process the job in a small fraction of the time it takes locally. Otherwise, I'd just run it locally.
If you built a ui that made it easier to use as part of the offering, it'd make sense for a lot of people.
Thanks!
I am looking explicitly for people who want to "run ffmpeg"
I don't have the skills, nor the capital, to build a solution for the whole market of people that want to mess with videos.
Just for reference Mix raised 177M since 2016.
The goal is not to run a startup, but a small business with recurrent business.
Of course there are a lot of way to approach this.
One would be an API sold at cost plus (which is the closest to my skillset.)
Building on top of that would be trivial for more pay-for-value product.
if you're the creator might I suggest an ai.txt like a robots.txt of all the content? so we can pass it to an LLM and use it to create custom commands we need based on real needs? that would be awesome!
Apparently it is still not part of the latest version of gohugo... we will get there.
I love ffmpeg, but yeah, some bits are a little ... obscure.
Right now, I am looking to normalize some audio without using ffmpeg-normalize, a popular Python package. Nothing against it on a personal level, I just ... want to know what is going on, and it's a lot of files and lines of code to do what is basically a two-pass process.
I have a growing interest in metadata and that's also a case which I do not find is often well-addressed.
Gotta leave this here for those that haven’t seen it :)
I've enjoyed using ffmpeg 1000% more since I was able to stop doing manually the tedious task of Googling for Stack Overflow answers and cobbling them into a command and got Chat GPT to write me commands instead.