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pages/_INFORM/ffmpeg.md
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@ -6,33 +6,22 @@ Essentials
### What?
[ffmpeg](https://ffmpeg.org/) is a swiss army knife for everything
audio/video. It can do practically every task under the sun, and in fact
powers most major dedicated \"video players\" (VLC, MPC-HC, built-in
players in Chrome and Firefox\...)[^1]
[ffmpeg](https://ffmpeg.org/) is a swiss army knife for everything audio/video. It can do practically every task under the sun, and in fact powers most major dedicated "video players" (VLC, MPC-HC, built-in players in Chrome and Firefox...)[^1]
### How?
If you\'re on Windows, it\'s technically possible to install `ffmpeg`
and use it directly [^2], but since the windows Command Prompt sucks ass
comfort-wise and scripting-wise, it\'s recommended to just [install
Ubuntu as part of the Windows Subsystem for
Linux](https://docs.microsoft.com/en-us/windows/wsl/install-win10), and
then `apt-get install ffmpeg`.
If you're on Windows, it's technically possible to install `ffmpeg` and use it directly [^2], but since the windows Command Prompt sucks ass comfort-wise and scripting-wise, it's recommended to just [install Ubuntu as part of the Windows Subsystem for Linux](https://docs.microsoft.com/en-us/windows/wsl/install-win10), and then `apt-get install ffmpeg`.
If you\'re on Linux, you already know what to do 8-)
If you're on Linux, you already know what to do 😎
Techniques
----------
(All commands are expected to be ran in `bash` or a similar Linux
shell.)
(All commands are expected to be ran in `bash` or a similar Linux shell.)
### Basic conversions
`ffmpeg` is pretty clever, it can correctly guess the codecs and
reasonable default settings by the file extension, so all of the
following will work as expected (and retain metadata[^3]!):
`ffmpeg` is pretty clever, it can correctly guess the codecs and reasonable default settings by the file extension, so all of the following will work as expected (and retain metadata[^3]!):
``` {.bash}
ffmpeg -i video.avi video.mp4
@ -43,10 +32,9 @@ ffmpeg -i song.flac song.mp3
#### mp3 bitrates
\"Reasonable\" might not be what you want though, especially in the case
of mp3, where the default bitrate is V4 (!), i.e. 140-185 kbps.
"Reasonable" might not be what you want though, especially in the case of mp3, where the default bitrate is V4 (!), i.e. 140-185 kbps.
If you want, for example, V[0]{.ul}, use the `-q:a`[^4] option, like so:
If you want, for example, V[0], use the `-q:a`[^4] option, like so:
``` {.bash}
ffmpeg -i song.flac -q:a 0 song.mp3
@ -56,13 +44,9 @@ More info at: <https://trac.ffmpeg.org/wiki/Encode/MP3>
#### video codecs
Since container/format ≠ codec, you might want to select the codec
manually.
Since container/format ≠ codec, you might want to select the codec manually.
While it can reasonably assumed that `mp4` ≅ `h264`, `avi` is a bit more
complex. You can list all the supported codecs with
`ffmpeg -codecs`[^5], but since there\'s several hundreds, you better
have an idea of what you want to do in the first place.
While it can reasonably assumed that `mp4` ≅ `h264`, `avi` is a bit more complex. You can list all the supported codecs with `ffmpeg -codecs`[^5], but since there's several hundreds, you better have an idea of what you want to do in the first place.
For example, if you want an `.avi` with xvid codec, you just do:
@ -72,8 +56,7 @@ ffmpeg -i original.mp4 -c:v libxvid output.avi
#### General codec options
This StackOverflow post explains everything:
<https://stackoverflow.com/a/20587693/3833159>
This StackOverflow post explains everything: <https://stackoverflow.com/a/20587693/3833159>
### video // image files // frames
@ -81,9 +64,7 @@ This StackOverflow post explains everything:
##### 1. creating a list of images
`ffmpeg` needs a list of images in a text file in a [specific
format](https://trac.ffmpeg.org/wiki/Concatenate#demuxer) in order to
convert them to a video. There\'s a couple ways to do this:
`ffmpeg` needs a list of images in a text file in a [specific format](https://trac.ffmpeg.org/wiki/Concatenate#demuxer) in order to convert them to a video. There's a couple ways to do this:
``` {.bash}
ls *.jpg | xargs -I xyz echo "file 'xyz'" > list.txt
@ -93,8 +74,7 @@ ls *.jpg | xargs -I xyz echo "file 'xyz'" > list.txt
for f in *.jpg; do echo "file '$f'" >> list.txt; done
```
It\'s up to preference, all end up with a list of all JPGs in current
directory, in `list.txt`.
It's up to preference, all end up with a list of all JPGs in current directory, in `list.txt`.
##### 2. list to video
@ -106,8 +86,7 @@ ffmpeg -f concat -r 30 -i list.txt out.mp4
`-r 30` specifies resulting FPS (30 FPS)
`out.mp4` is output file - autodetected as h264-encoded. (`out.avi`,
`out.gif`, etc. also work - refer to ffmpeg manual)
`out.mp4` is output file - autodetected as h264-encoded. (`out.avi`, `out.gif`, etc. also work - refer to ffmpeg manual)
#### video -&gt; images
@ -115,16 +94,11 @@ ffmpeg -f concat -r 30 -i list.txt out.mp4
ffmpeg -i FILE image%05d.png
```
Where `FILE` is the video file, and `image%05d.png` is the format string
for image filenames; this will create `image00001.png`,
`image00002.png`, `image00123.png`, etc. (`%05d` means pad with `5`
zeroes; `%010d` for padding with `10` zeroes\...)
Where `FILE` is the video file, and `image%05d.png` is the format string for image filenames; this will create `image00001.png`, `image00002.png`, `image00123.png`, etc. (`%05d` means pad with `5` zeroes; `%010d` for padding with `10` zeroes...)
### Streams
`ffmpeg` can also smoothly handle streams, so basic stream capture is
pretty trivial, provided you grabbed the playlist/HLS url from
somewhere[^6]:
`ffmpeg` can also smoothly handle streams, so basic stream capture is pretty trivial, provided you grabbed the playlist/HLS url from somewhere[^6]:
``` {.bash}
ffmpeg -i "https://example.com/playlist.m3u8" my_stream.mp4
@ -132,9 +106,7 @@ ffmpeg -i "https://example.com/playlist.m3u8" my_stream.mp4
#### Taking a screenshot of a stream
`-vframes 1` is the option that tells `ffmpeg` to just capture one (i.e.
the first) frame of the video - in the case of streams, this means the
latest one anyway.
`-vframes 1` is the option that tells `ffmpeg` to just capture one (i.e. the first) frame of the video - in the case of streams, this means the latest one anyway.
``` {.bash}
ffmpeg -i "https://example.com/playlist.m3u8" -vframes 1 capture.jpg
@ -142,37 +114,16 @@ ffmpeg -i "https://example.com/playlist.m3u8" -vframes 1 capture.jpg
### dropped frame re-interpolation
`ffmpeg` also has a [rich set of
filters](https://ffmpeg.org/ffmpeg-filters.html), two of which are of
interest for us now:
`ffmpeg` also has a [rich set of filters](https://ffmpeg.org/ffmpeg-filters.html), two of which are of interest for us now:
- [mpdecimate](https://ffmpeg.org/ffmpeg-filters.html#mpdecimate) -
*Drop frames that do not differ greatly from the previous frame in
order to reduce frame rate.*
- [minterpolate](https://ffmpeg.org/ffmpeg-filters.html#minterpolate) -
*Convert the video to specified frame rate using motion
interpolation.*
- [mpdecimate](https://ffmpeg.org/ffmpeg-filters.html#mpdecimate) - *Drop frames that do not differ greatly from the previous frame in order to reduce frame rate.*
- [minterpolate](https://ffmpeg.org/ffmpeg-filters.html#minterpolate) - *Convert the video to specified frame rate using motion interpolation.*
The idea is that `mpdecimate` drops all near-duplicate frames, and
`minterpolate` re-calculates them using non-duplicate frames that were
left.
The idea is that `mpdecimate` drops all near-duplicate frames, and `minterpolate` re-calculates them using non-duplicate frames that were left.
`mpdecimate`\'s defaults are pretty okay, but the result may not look
too good if the frame drops are frequent and long. I\'ve had pretty good
results using its `max` parameter which limits the amount of frames
dropped in a single stretch of video, e.g. `-vf mpdecimate=max=15` which
drops at most 15 frames (i.e. half a second assuming 30 FPS), meaning
interpolation won\'t happen everywhere and the video will remain
faithfully choppy.
`mpdecimate`'s defaults are pretty okay, but the result may not look too good if the frame drops are frequent and long. I've had pretty good results using its `max` parameter which limits the amount of frames dropped in a single stretch of video, e.g. `-vf mpdecimate=max=15` which drops at most 15 frames (i.e. half a second assuming 30 FPS), meaning interpolation won't happen everywhere and the video will remain faithfully choppy.
`minterpolate`, on the other hand, defaults to semi-smart motion
compensated interpolation, and that *might* just be what you want, but
it generally gives pretty funky results. Fortunately, it also has a
\"blend\" mode, which just averages the start and end frames and
crossfades them, which gives much more agreeable outputs for simple
frame drop situations. It is also generally much faster, I was getting
near or above real-time speeds using \"blend\", whereas motion
compensation dropped the processing speed to 0.01x.
`minterpolate`, on the other hand, defaults to semi-smart motion compensated interpolation, and that *might* just be what you want, but it generally gives pretty funky results. Fortunately, it also has a "blend" mode, which just averages the start and end frames and crossfades them, which gives much more agreeable outputs for simple frame drop situations. It is also generally much faster, I was getting near or above real-time speeds using "blend", whereas motion compensation dropped the processing speed to 0.01x.
**TL;DR**: Full command(s) including the filter pipeline:
@ -187,33 +138,9 @@ ffmpeg -i choppy_video.mp4 -vf mpdecimate=max=10,minterpolate=mi_mode=blend smoo
ffmpeg -i choppy_video.mp4 -vf mpdecimate,minterpolate smoother_video.mp4
```
ffmpeg - skipping - remove duplicate frames after effects
#### what is \`N/FRAME\_RATE/TB\`
- except the use of \`FRAME\_RATE\` variable the \`N/FRAME\_RATE/TB\`
is equal to the example below from ffmpeg documentation
(\[source\](<https://ffmpeg.org/ffmpeg-filters.html#Examples-123>))
*
> Set fixed rate of 25 frames per second:
> `setpts=N/(25*TB)`
- the math behind it perfectly explained in What is video timescale,
timebase, or timestamp in ffmpeg?
* it basically calculates timestamp for each frame and multiplies it with timebase `TB` to enhance precision
### mp4 compatibility
h264 also has \"profiles\", basically [sets of
features](https://en.wikipedia.org/wiki/Advanced_Video_Coding#Profiles)
- and it turns out this can make the difference between a file working
and not working on some crappy embedded media players, like TVs or pico
projectors.
h264 also has "profiles", basically [sets of features](https://en.wikipedia.org/wiki/Advanced_Video_Coding#Profiles) - and it turns out this can make the difference between a file working and not working on some crappy embedded media players, like TVs or pico projectors.
> > The `-profile:v` option limits the output to a specific H.264
> > profile. Some devices (mostly very old or obsolete) only support the
@ -226,9 +153,7 @@ projectors.
ffmpeg -i original.mp4 -profile:v baseline output.mp4
```
And apparently, some players are also sensitive to the pixel format[^7],
i.e. can\'t handle anything else than YUV w/ 4:2:0 chroma subsampling,
to fix this use the `-pix_fmt` option as follows:
And apparently, some players are also sensitive to the pixel format[^7], i.e. can't handle anything else than YUV w/ 4:2:0 chroma subsampling, to fix this use the `-pix_fmt` option as follows:
``` {.bash}
ffmpeg -i original.mp4 -pix_fmt yuv420p output.mp4
@ -236,15 +161,17 @@ ffmpeg -i original.mp4 -pix_fmt yuv420p output.mp4
ffmpeg -i original.mp4 -profile:v baseline -pix_fmt yuv420p output.mp4
```
No silver bullet, you\'ll just have to try different things for
different devices. A database of crappy players and appropriate `ffmpeg`
settings would be great.
No silver bullet, you'll just have to try different things for different devices. A database of crappy players and appropriate `ffmpeg` settings would be great.
### random
<https://ottverse.com/ffmpeg-drawtext-filter-dynamic-overlays-timecode-scrolling-text-credits/>
[^1]: <https://en.wikipedia.org/wiki/FFmpeg#Projects_using_FFmpeg>
---
# Footnotes
[^1]: See https://en.wikipedia.org/wiki/FFmpeg#Projects_using_FFmpeg
[^2]: from <https://ffmpeg.zeranoe.com/builds/>
@ -254,8 +181,6 @@ settings would be great.
[^5]: and respectively, formats with `ffmpeg -formats`
[^6]: like
<https://addons.mozilla.org/en-US/firefox/addon/hls-stream-detector/>;
or just press F12, check the Network tab, and look carefully
[^6]: like <https://addons.mozilla.org/en-US/firefox/addon/hls-stream-detector/>; or just press F12, check the Network tab, and look carefully
[^7]: <https://trac.ffmpeg.org/wiki/Encode/H.264#Encodingfordumbplayers>
[^7]: From: https://trac.ffmpeg.org/wiki/Encode/H.264#Encodingfordumbplayers