[FFmpeg-devel] [PATCH] avformat/flvdec: RtmpSampleAccess no longer breaks stream detection

[Peter van der Spek]

It took me some time to figure out where this |RtmpSampleAccess packet came from. It turns out that this is an undocumented AMF packet that is used to transfer the state of the documented Client.audioSampleAccess and Client.videoSampleAccess state to the client.

This post gave me some clues: https://nicolas.brousse.info/blog/flash-how-to-fix-the-security-sandbox-violation-bitmapdata-draw/

These sampleAccess states are used to allow a (Flash) client to access the raw video and audio data. The states are pushed by the server as a IRtmpSampleAccess packet.

Adobe FMS, Wowza, Red5, etc… all support this mechanism.

I’m able to reproduce this issue with RTMP streams pulled from a Nginx-RTMP server (https://github.com/arut/nginx-rtmp-module).

Client.audioSampleAccess and Client.videoSampleAccess are documented here:
https://helpx.adobe.com/adobe-media-server/ssaslr/client-class.html#client_audiosampleaccess
https://helpx.adobe.com/adobe-media-server/ssaslr/client-class.html#client_videosampleaccess

Best,
Peter
On 18 Aug 2020, 14:46 +0200, Michael Niedermayer <michael at niedermayer.cc>, wrote:
>
> Do you have a testcase?
> Is this documented somewhere?
>
> thx
>
> [...]
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