Normalize videos and audio files to a standardized frame rate and quality to minimize the file size while maintaining adequate quality for video projection.
| Property | Default Video | Tutorial Video |
|---|---|---|
| Height | 720p | 720p |
| Video bitrate | 2 Mbps | 500 kbps |
| Frame rate | 25 fps | 10 fps |
| Audio bitrate | 128 kbps | 128 kbps |
$ snap install squeeze-vid
$ squeeze-vid --help
usage: -c [-h] [-a] [-c] [-i] [-k TRIM TRIM] [-m RATE_CONTROL_MODE] [-n] [-s SPEED] [-t] [-v] [-V] [--av1] [--video_encoder VIDEO_ENCODER] [file [file ...]]
Convert video file to MP4, ensuring baseline video quality:
* Default: 720p, CRF=27 (H.264), 25 fps for projected video
* Tutorial: Only use 10 fps for tutorial video
Also perform other useful operations on media files.
positional arguments:
file space-separated list of media files to modify
optional arguments:
-h, --help show this help message and exit
-a, --audio convert file(s) to MP3 audio
-c, --command print the equivalent ffmpeg bash command and exit
-i, --info show stream properties of given file (only 1 accepted)
-k TRIM TRIM, --trim TRIM TRIM
trim the file to keep content between given timestamps (HH:MM:SS)
-m RATE_CONTROL_MODE, --rate-control-mode RATE_CONTROL_MODE
specify the rate control mode [CRF]: CBR, CRF; if CBR is specified, the video bitrate is set to 2Mbps
-n, --normalize normalize video reslution, bitrate, and framerate; this is the default action if no options are given
-s SPEED, --speed SPEED
change the playback speed of the video using the given factor (0.5 to 100)
-t, --tutorial use lower bitrate and fewer fps for short tutorial videos
-v, --verbose give verbose output
-V, --version show version number and exit
--av1 shortcut to use libsvtav1 video encoder
--video_encoder VIDEO_ENCODER
specify video encoder [libx264]: libx264, libsvtav1, libvpx-vp9
- "HD" video has 2 resolutions: 720p and 1080p. (Note: 4K is actually "2160p".)
- Framerates can vary from 24 fps (film) to 30 fps (common streaming) to 60 fps (fast-paced video) and higher.
- Video bitrate can vary from 500 kbps to 8 Mbps or more.
- Audio bitrate can vary from 96 kbps to over 1,400 kbps.
Assuming mediocre projector quality and internet bandwidth, 720p video strikes a reasonable balance between picture size and file size.
Assuming that most content consists of presentations with a slow pace, 25 fps seems to be a sufficient framerate.
Testing conversion quality with ffmpeg-quality-metrics has shown that CRF=27 is comparable in visual quality to 2 Mbps video bitrate while typically producing a smaller file size. So squeeze-vid has recently begun using CRF=27 as the default quality setting for H.264 encoded videos rather than setting a maximum/average bitrate. AV1 and VP9 encodings use a proportionally equivalent factor based on their own scales.
For 720p 30fps video, bitrate recommendations range from 500 Kbps to 4 Mbps. Personal experience has led to choosing a bitrate of 2 Mbps in an attempt to balance the tensions between filesize and perceived quality.
YouTube audio has chosen to stream AAC files at 126 kbps. At 128 kbps, one can expect to use about 1 MB of storage space for every 1 minute of audio. This seems like a reasonable value for our purposes.
References