Table of Contents
Codecs supported
Video:
- H264
- VP8
- H265 (since build 5.2.1803)
Audio:
- Opus
- AAC
- G711 (PCMA, PCMU)
- G722
The cases when transcoding is enabled
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In this case stream will be transcoded to picture width and height that are requested by subscriber. If subscriber does not set picture height, it wiil be set to 120. If If subscriber does not set picture width, it wiil will be set to 160.
Transcoder output stream audio and video synchronization
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Picture width alignment while preserving a picture aspect ratio
Since build 5.2.1842 it is possible to set a picture width alignment when aspect ratio preserving is enabled. By default, a picture width will be rounded down:
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video_transcoder_round_ratio=0 |
For example, if 1280x720 stream is transcoded to 480p resolution, the picture resolution will be 852x480 by default. The parameter
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video_transcoder_round_ratio=1 |
enables the picture width rounding up: in this case the resolution will be 854x480.
Vertical video aspect ratio calculation
Since build 5.2.1911, WCS detects a stream published orientation by picture width and height and keeps aspect ratio as follows:
1. For horizontal (landscape) video (a picture width is greater than or equal to height) the height
value of transcoding profile will be applied to picture height, a picture width to transcode will be calculated by picture height. For example, a source stream with 1920x1080 (16:9) resolution will be transcoded to 640x360 resolution by profile with height: 360
.
2. For vertical (portrait) video (a picture width is less than height) the height
value of transcoding profile will be applied to picture width, a picture heignht to transcode will be calculated by picture width. For example, a source stream with 1080x1920 (9:16) resolution will be transcoded to 360x640 resolution by profile with height: 360
.
Transcoder output stream audio and video synchronization
By default transcoder does not synchronize output stream audio and video, leaving sinchronization value as is. This can lead to out of audio and video sync in stream transcoded. To prevent this, the pacer buffer is added in build 5.2.543 which can be enabled with the following parameter
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encoder_priority=FF |
2. Default watermark (black picture) will be used if watermark file is damaged or absent
Symptoms: black picture in output stream when watermark is added, there is a message in server log
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Wrong watermark file format. Should be PNG. |
Solution: use only correct PNG file to add watermark