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| Parameter | Values available | Description |
|---|---|---|
| Audio parameters | ||
| codec | opus mpeg4-generic speex ulaw | Audio codec to use |
| bitrate | Depends on quality required and bandwidth available | Audio bitrate, bps |
| rate | 8000 11025 12000 16000 22050 24000 32000 44100 48000 | Audio sample rate, kHz |
| channels | 1 2 | Channels quantity: mono or stereo |
| Video parameters | ||
| codec | h264 mpv vp8 | Video codec to use |
| bitrate | Depends on quality required and bandwidth available | Video bitrate, kbps |
| width | Depends on quality required and bandwidth available | Picture width |
| height | Depends on quality required and bandwidth available | Picture height |
| codeImpl | FF OPENH264 | Video codec used: based on FFmpeg or OpenH.264, FF by default |
| gop | Depends on quality required and bandwidth available | Key frames frequency (GOP) |
| fps | Depends on quality required and bandwidth available | Frames frequency per second |
| quality | Depends on quality required and bandwidth available | Video quality |
| preset | ultrafast superfast veryfast faster fast medium slow slower veryslow placebo | FFmpeg FF preset, ultrafast by default |
| profile | Depends on required quality | FFmpeg FF profile, Baseline by default |
| level | Depends on required quality | FFmpeg FF level, 3.1 by default |
If picture width is not set or equal to 0, video will be scaled by height with aspect ratio preserving.
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FFmpeg parameters management
When using FFmpeg FF codec implementation, encoding preset, profile and level can be set. For example, the following parameters
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| Code Block | ||
|---|---|---|
| ||
cdn_force_version=2.2 |
Known issues
1. When FFmpeg based FF encoder imp;lementation is used, there can be distortions (macroblocks) in first frames of stream transcoded
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| Code Block | ||||
|---|---|---|---|---|
| ||||
profiles:
-240p:
audio:
codec : opus
rate : 48000
video:
height : 240
gop : 50
fps : 25
codec : h264
preset : veryfast
quality : 25
codecImpl : FF |
b) use OpenH264 OPENH264 encoder implementation if it is necessary to keep specified video bitrate
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