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Below is the call flow when capturing an RTMP stream from another server

Known issues


Excerpt

1. A stream containing B-frames does not play or plays with artifacts (latencies, lags)

Symptoms:

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  • a stream sent by the

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  • RTMP encoder does not play or plays with latencies or lags
  • warnings in

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09:32:31,238 WARN 4BitstreamNormalizer - RTMP-pool-10-thread-5 It is B-frame!

Solution:

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2. When recording the captured stream to the disk, only audio is recorded

Symptoms: when the "record": "true" parameter is set in the /pull/rtmp/pull REST query, the received file lacks video track, only audio is present.
Solution: in the SDP setting set the

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a=sendonly

attribute for the video track.

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change the encoder settings so, that B-frames were not used (lower encoding profile, specify in the command line etc).

2. AAC frames of type 0 are not supported by decoder and will be ignored while stream pulled playback

In this case, warnings will be

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displayed in the client log:

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10:13:06,815 WARN AAC - AudioProcessor-c6c22de8-a129-43b2-bf67-1f433a814ba9 Dropping AAC frame that starts with 0, 119056e500

3. When publishing and then playing and recording H264 + AAC stream video may be out of sync with sound, or no sound at all.

Symptoms: when playing H264 + AAC stream published on server, and when recordingsuch stream, sound is out of sync with video or absent

Solution: set the following parameter in flashphoner.properties file

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disable_drop_aac_frame=true

This parameter also turns off AAC frames dropping.

4. Sound may be distorted or absent when resampled to 11025 Hz

Symptoms: when H264 + AAC stream published on WCS server is played with AAC sample rate 11025 Hz, sound is distorted or absent

Solution: do not use 11025 Hz sample rate, or escape AAC sound resampling to this rate, for example, do not set this sample rate in SDP settings.

5. Some RTMP functions does not supported and will be ignored:

  • FCSubscribe
  • FCPublish
  • FCUnpublish
  • onStatus
  • onUpstreamBase
  • releaseStream

6. When recording the captured stream to the disk, only audio is recorded

Symptoms: when the "record": "true" parameter is set in the /pull/rtmp/pull REST query, the received file lacks video track, only audio is present.
Solution: in the SDP settings set the

Code Block
languagebash
themeRDark
a=sendonly

attribute for the video track.