[FFmpeg-trac] #10578(avformat:new): send RTSP keep alive even when paused

[FFmpeg]

#10578: send RTSP keep alive even when paused
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             Reporter:  tmc2001      |                    Owner:  (none)
                 Type:  defect       |                   Status:  new
             Priority:  normal       |                Component:  avformat
              Version:  unspecified  |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Description changed by tmc2001:

Old description:

> Workflow:
> 1. Have a RTSP server that supports Pause.
> 2. Have ffmpeg play a video from that server (rtsp://<ipaddr>:...).
> 3. Pause the video in ffmpeg (call av_read_pause)
> 4. ffmpeg does NOT properly send the keep alive when Paused
> (either "GET_PARAMETER" or "OPTIONS"). This is the bug.
> 5. Since the RTSP server expects the keep alive, after the specified
> timeout (usually 60s) it closes the connection.
>

> The bug is in:
> File: libavformat/rtspdec.c
> Method: rtsp_read_packet
>
> This method first does ff_rtsp_fetch_packet, which fails when the server
> is Paused, causing it to never send the "GET_PARAMETER" or "OPTIONS"
> which is placed immediately after this call.
>

> Potential easy fix:
> Simply move that block of code before ff_rtsp_fetch_packet.
>
> That is, move the entire if block:
> if (!(rt->rtsp_flags & RTSP_FLAG_LISTEN)) { ... }
>
> just before the call to:
> ret = ff_rtsp_fetch_packet(s, pkt);
>

> I have tested this and it seems to work well for our cases.
> Sent this to ffmpeg-devel mailing list as well:
> http://ffmpeg.org/pipermail/ffmpeg-devel/2023-August/313608.html
>

> Would appreciate if an experienced DEV would approve and integrate into
> ffmpeg.
> Thank you.

New description:

 Workflow:
 1. Have a RTSP server that supports Pause.
 2. Have ffmpeg play a video from that server (rtsp://<ipaddr>:...).
 3. Pause the video in ffmpeg (call av_read_pause)
 4. ffmpeg does NOT properly send the keep alive when Paused (either
 "GET_PARAMETER" or "OPTIONS"). This is the bug.
 5. Since the RTSP server expects the keep alive, after the specified
 timeout (usually 60s) it closes the connection.


 The bug is in:
 File: libavformat/rtspdec.c
 Method: rtsp_read_packet

 This method first does ff_rtsp_fetch_packet, which fails when the server
 is Paused, causing it to never send the "GET_PARAMETER" or "OPTIONS" which
 is placed immediately after this call.


 Potential easy fix:
 Simply move that block of code before ff_rtsp_fetch_packet.

 That is, move the entire if block:
 if (!(rt->rtsp_flags & RTSP_FLAG_LISTEN)) { ... }

 just before the call to:
 ret = ff_rtsp_fetch_packet(s, pkt);


 I have tested this and it seems to work well for our cases.
 Sent this to ffmpeg-devel mailing list as well:
 http://ffmpeg.org/pipermail/ffmpeg-devel/2023-August/313608.html


 Would appreciate if an experienced DEV would approve and integrate into
 ffmpeg.
 Thank you.

--
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Ticket URL: <https://trac.ffmpeg.org/ticket/10578#comment:1>
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