https://github.com/pcolby/cycliq
Just some scripts for working with video from Cycliq cameras
https://github.com/pcolby/cycliq
cycling cycliq ffmpeg
Last synced: 3 months ago
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Just some scripts for working with video from Cycliq cameras
- Host: GitHub
- URL: https://github.com/pcolby/cycliq
- Owner: pcolby
- Created: 2020-04-28T11:18:02.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2020-05-18T09:43:01.000Z (about 5 years ago)
- Last Synced: 2025-01-17T13:51:19.493Z (5 months ago)
- Topics: cycling, cycliq, ffmpeg
- Language: Shell
- Homepage:
- Size: 18.6 KB
- Stars: 1
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Cycliq
Just some scripts for working with [Cycliq] camera videos.
## Background
Cycliq camera videos contain two streams within an MP4 container:
* Video: H264, with configurable resolution and frame-rate (eg 1920x1080, 60 FPS).
* Audio: FLY12CE: LPCM, 16-bit, signed, little endian, 48kHz, stereo (1,535 kb/s).
* Audio: FLY6CE: LPCM, 16-bit, signed, little endian, 44.1kHz, stereo (1,411 kb/s).
Just an example:
```sh
$ ffprobe /path/to/cycliq/video.mp4 2>&1 | grep Stream
Stream #0:0(eng): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 28204 kb/s, 59.94 fps, 59.94 tbr, 60k tbn, 119.88 tbc (default)
Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, 2 channels, s16, 1536 kb/s (default)
```
Note, however, that ISO standards do **not** officially allow LPCM in MP4 containers.
For this reason, FFmpeg will happily read such containers, but [not write them][1].
## Concatenate
The Cycliq video cameras automatically split sessions into multiple video files
(to make the file "more manageable"). The `concat.sh` script here can be used to join
those files into a single video.
Basic usage:
```sh
./concat.sh input1.mp4 input2.mp4 [... inputN.mp4] output.mp4
```
Depending on your shell, you may be able to use sequence expressions in [brace
expansion][3] to simply the input filenames, such as:
```sh
./concat.sh /media/.../DCIM/100_CF12/CYQ_000{1..5}.MP4 output.mp4
```
### Environment Variables
The `concat.sh` script's behaviour can be modified by setting the following
environment variables:
* `AUDIO_FLAGS` - overrides the default audio codec; see [Audio](#Audio) below.
* `SPEED_UP` - overrides the playback speed; see [Speed-up](#Speed-up) below.
### Output Codecs
By default, `concat.sh` attempts to most lossless codecs possible, but lossless
copying is not always possible. See the [Audio](#Audio) and [Speed-up](#Speed-up)
sections below for more details, but the following table summarised the *default*
output codecs the script chooses.
| Speed | Container | Audio | Video |
| :---: | :-------: | :---: | :---: |
| Original | Matroska (mkv) | LPCM (lossless copy) | H.264 (lossless copy) |
| Original | MPEG-4 (mp4) | AAC-LC 384kpbs | H.264 (lossless copy) |
| Sped-up | Matroska (mkv) | AAC-LC 384kpbs | H.264 (re-encoded) |
| Sped-up | MPEG-4 (mp4) | AAC-LC 384kpbs | H.264 (re-encoded) |
### Audio
The audio stream included in the output video file is defined by the `AUDIO_FLAGS` environment
variable. This can be set to any valid set of FFmpeg flags. However, the defaults are pretty
sensible.
The default for all non-MP4 outputs (eg Matroska) without speed-up, is `-c:a copy`, which
will copy the original PCM audio stream verbatim (ie losslessly). However, as noted in the
[background](#Background) section above, FFmpeg will not write MP4 containers with PCM
audio. For this reason, if the output is an `*.mp4` file, then `AUDIO_FLAGS` defaults to:
`-c:a aac -profile:a aac_low -b:a 384k`
That is, the audio stream will be converted (from 16-bit steroe PCM) to AAC Low Complexity
at 384 kbps. This default was chosen to match [YouTube's recommendation][2], since uploading
to YouTube is a common use-case, but of course this be overridden (by setting `AUDIO_FLAGS`)
if desired.
For example, to use FLAC, do something like:
```sh
AUDIO_FLAGS='-c:a flac' ./concate.sh ... output.mkv
```
### Speed-up
The video can be sped-up by setting the `SPEED_UP` environment variable to the 'times'
speed-up you want. For example, setting `SPEED_UP` to `8`, will result in a video that
plays 8 times faster than the original.
For example:
```sh
SPEED_UP=8 ./concat ...
```
Due to the way FFmpeg filters work, the speed-up only works in powers of two, so if
`SPEED_UP` is set to something other than a power of two, the nearest power of two will
be used instead. For example, if `SPEED_UP` is set to `5`, then the resulting video will
be four times faster, since 4 is nearest power of two to 5.
Also note, that since speeding up the audio (while keeping the original pitch) requires
the audio to be re-encoded, lossless audio is not possible in this mode. In this case the
script defaults to AAC (the same default specified for MP4 output in the [Audio](#Audio)
secition above) though a lossless output codec, such as LPCM, can still be specified
by the `AUDIO_FLAGS` variable if desired.
## Addendum
Just some rough, random notes...
A quick, hacky way to check which (if any) lossless audio codecs FFmpeg supports for any
given *output* container:
```sh
for CODEC in $(ffmpeg -codecs 2>&1 | grep '^ .EA..S' | cut -d' ' -f3); do
echo ">> $CODEC"
ffmpeg -y -v error -i small-test-video.mp4 -c:a "$CODEC" -c:v copy "test-$CODEC.mp4"
done
ls -lrS *.mp4
```
So, for example, for FFmpeg 4.1.4, no lossless codecs are supported for MP4 containers
(without enabling experimental features). And the following are supported for Matroska
containers: `alac`, `flac`, `tta`, `wavpack`, and a bunch of `pcm_*` formats.
For what its worth, `*.mkv` files with any of those four lossless compression formats
work fine with both YouTube and VLC. I didn't bother trying the PCM formats with YouTube,
but some (floating point PCM formats?) don't work with VLC.
### To do
* Consider changing the default `mp4` audio codec to MPEG4-ALS if/when FFmpeg supports
it (currently FFmpeg can *decode*, but not *encode* ALS).
* Consider changing the default audio codec for sped-up `mkv` output to something
lossless (perhaps ALAC?).
[1]: https://trac.ffmpeg.org/ticket/3818
[2]: https://support.google.com/youtube/answer/1722171?hl=en
[3]: https://www.gnu.org/software/bash/manual/html_node/Brace-Expansion.html#Brace-Expansion
[Cycliq]: https://cycliq.com/