2023-12-25-notes.txt

[x] accept multiple filename args
[x] sanity check filenames and base times
[x] merge matching audio and video files in output
[x] more quiet ffmpeg
[x] configure tmp directory
[x] configure output directory
[x] create unique tmp filenames
[x] configure framerate, bitrate, resolution
[ ] --requirements arg to aid in setup


----

feature requests
  - process all files given on the command line
  - default mode: pad and resample individual file transforms
  - force transcoded video file to specific resolution (otherwise the first frame sets the resolution)
  - configure framerate and bitrate of output file (otherwise maybe default to 30fps and 5mbs)
  - configurable tmp directory
  - configurable output directory
  - mode: pair audio and video files in output
  - mode: configurable canvas size and multi-track layout geometry



1703174279145-02ce3bcb-bf5b-423f-9699-63fca113a952-cam-audio-1703174279270.webm


----

count number of frames

```
ffprobe -i video.mpg -show_frames -show_entries frame=best_effort_timestamp_time -of csv=p=0 -v quiet | wc -l
```

----

resizing gives us a better video quality if the first frame is not 1280x720 (duh)

```
ffmpeg -y -i nina-5fea61e5-cam-video.webm -vf scale=1280:720 -r 30 -b:v 5000k video.mpg
```

----

concat

It would be good to use the concat protocol, which works at the file level. This
allows copying of all video frames without re-encoding. So a possible approach.

1. generate an mp4 for the padding, in a .ts container
2. transcode the rtp video webm to mp4, in a .ts container
3. concat the two files into an mp4 container

```
# 1
ffmpeg -y -f lavfi -i "color=c=black:s=1280x720" -t 10 -r 30 -b:v 5000k -c:v libx264 tmp-padding.ts
# 2 
ffmpeg -y -i nina-5fea61e5-cam-video.webm -r 30 -vf scale=1280:720 -b:v 5000k -c:v libx264 tmp-video.ts


# 
ffmpeg -i "concat:tmp-padding.ts|tmp-video.ts" -c copy output.mp4
 ```


From the ffmpeg docs
```
ffmpeg -i input1.mp4 -c copy intermediate1.ts
ffmpeg -i input2.mp4 -c copy intermediate2.ts
ffmpeg -i "concat:intermediate1.ts|intermediate2.ts" -c copy output.mp4
```