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My company has a bunch of IP cameras that we distribute - specifically Grandstream - and the manufacturer has changed their firmware. The normal keepalive that ffmpeg uses for the rtsp streams ( either ff_rtsp_send_cmd_async(s, "GET_PARAMETER", rt->control_uri, NULL); or ff_rtsp_send_cmd_async(s, "OPTIONS", "*", NULL); both in in libavformat/rtspdec.c) is no longer working, for two reasons:

1) The new Grandstream firmware is now checking for a receiver report to determine whether or not the program reading the stream is live, not just anything.

2) The new Grandstream firmware requires that the receiver report to keep the connection alive happen at least once every 25 seconds, and on the audio stream it is currently only happening about every 30 seconds or so (video is getting it every 7 seconds or so).

So after about a minute with ffmpeg connected, the camera stops sending the audio stream, the audio stream on ffmpeg reads end-of-file, and then ffmpeg shuts everything down.

As I can't change the firmware, I'm trying to dig through the ffmpeg code to make it send the appropriate receiver report for the keep alive... but I am getting nowhere. I've added a little snippet of code into the receiver reports so I know when they're running when I call ffmpeg on debug, but... well, it's not going well.

Test command: ffmpeg -loglevel debug -i rtsp://admin:admin@192.168.4.3:554/0 -acodec libmp3lame -ar 22050 -vcodec copy -y -f flv /dev/null &> test.txt

Test output:

`[root@localhost ffmpeg]# cat test.txt
ffmpeg version 2.0 Copyright (c) 2000-2013 the FFmpeg developers
  built on Aug 21 2013 14:24:28 with gcc 4.4.7 (GCC) 20120313 (Red Hat 4.4.7-3)
  configuration: --datadir=/usr/share/ffmpeg --bindir=/usr/local/bin --libdir=/usr/local/lib --incdir=/usr/local/include --shlibdir=/usr/lib --mandir=/usr/share/man --disable-avisynth --extra-cflags='-O2 -g -pipe -Wall -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -m32 -march=i386 -mtune=generic -fasynchronous-unwind-tables' --enable-avfilter --enable-libx264 --enable-gpl --enable-version3 --enable-postproc --enable-pthreads --enable-shared --enable-swscale --enable-vdpau --enable-x11grab --enable-librtmp --enable-libopencore-amrnb --enable-libopencore-amrwb --disable-static --enable-libgsm --enable-libxvid --enable-libvpx --enable-libvorbis --enable-libvo-aacenc --enable-libmp3lame
  libavutil      52. 38.100 / 52. 38.100
  libavcodec     55. 18.102 / 55. 18.102
  libavformat    55. 12.100 / 55. 12.100
  libavdevice    55.  3.100 / 55.  3.100
  libavfilter     3. 79.101 /  3. 79.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Splitting the commandline.
Reading option '-loglevel' ... matched as option 'loglevel' (set logging level) with argument 'debug'.
Reading option '-i' ... matched as input file with argument 'rtsp://admin:admin@192.168.4.3:554/0'.
Reading option '-acodec' ... matched as option 'acodec' (force audio codec ('copy' to copy stream)) with argument 'libmp3lame'.
Reading option '-ar' ... matched as option 'ar' (set audio sampling rate (in Hz)) with argument '22050'.
Reading option '-vcodec' ... matched as option 'vcodec' (force video codec ('copy' to copy stream)) with argument 'copy'.
Reading option '-y' ... matched as option 'y' (overwrite output files) with argument '1'.
Reading option '-f' ... matched as option 'f' (force format) with argument 'flv'.
Reading option '/dev/null' ... matched as output file.
Finished splitting the commandline.
Parsing a group of options: global .
Applying option loglevel (set logging level) with argument debug.
Applying option y (overwrite output files) with argument 1.
Successfully parsed a group of options.
Parsing a group of options: input file rtsp://admin:admin@192.168.4.3:554/0.
Successfully parsed a group of options.
Opening an input file: rtsp://admin:admin@192.168.4.3:554/0.
[rtsp @ 0x9d9ccc0] SDP:
v=0
o=StreamingServer 3331435948 1116907222000 IN IP4 192.168.4.3
s=h264.mp4
c=IN IP4 0.0.0.0
t=0 0
a=control:*
m=video 0 RTP/AVP 96
a=control:trackID=0
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1; sprop-parameter-sets=Z0LgHtoCgPRA,aM4wpIA=
m=audio 0 RTP/AVP 0
a=control:trackID=1
a=rtpmap:0 PCMU/8000
a=ptime:20
m=application 0 RTP/AVP 107
a=control:trackID=2
a=rtpmap:107 vnd.onvif.metadata/90000


[rtsp @ 0x9d9ccc0] video codec set to: h264
[NULL @ 0x9d9f400] RTP Packetization Mode: 1
[NULL @ 0x9d9f400] Extradata set to 0x9d9f900 (size: 22)!
[rtsp @ 0x9d9ccc0] audio codec set to: pcm_mulaw
[rtsp @ 0x9d9ccc0] audio samplerate set to: 8000
[rtsp @ 0x9d9ccc0] audio channels set to: 1
[rtsp @ 0x9d9ccc0] hello state=0
[h264 @ 0x9d9f400] Current profile doesn't provide more RBSP data in PPS, skipping
    Last message repeated 1 times
[rtsp @ 0x9d9ccc0] All info found
Guessed Channel Layout for  Input Stream #0.1 : mono
Input #0, rtsp, from 'rtsp://admin:admin@192.168.4.3:554/0':
  Metadata:
    title           : h264.mp4
  Duration: N/A, start: 0.000000, bitrate: 64 kb/s
    Stream #0:0, 28, 1/90000: Video: h264 (Constrained Baseline), yuv420p, 640x480, 1/180000, 10 tbr, 90k tbn, 180k tbc
    Stream #0:1, 156, 1/8000: Audio: pcm_mulaw, 8000 Hz, mono, s16, 64 kb/s
Successfully opened the file.
Parsing a group of options: output file /dev/null.
Applying option acodec (force audio codec ('copy' to copy stream)) with argument libmp3lame.
Applying option ar (set audio sampling rate (in Hz)) with argument 22050.
Applying option vcodec (force video codec ('copy' to copy stream)) with argument copy.
Applying option f (force format) with argument flv.
Successfully parsed a group of options.
Opening an output file: /dev/null.
Successfully opened the file.
detected 2 logical cores
[graph 0 input from stream 0:1 @ 0x9f15380] Setting 'time_base' to value '1/8000'
[graph 0 input from stream 0:1 @ 0x9f15380] Setting 'sample_rate' to value '8000'
[graph 0 input from stream 0:1 @ 0x9f15380] Setting 'sample_fmt' to value 's16'
[graph 0 input from stream 0:1 @ 0x9f15380] Setting 'channel_layout' to value '0x4'
[graph 0 input from stream 0:1 @ 0x9f15380] tb:1/8000 samplefmt:s16 samplerate:8000 chlayout:0x4
[audio format for output stream 0:1 @ 0x9efa7c0] Setting 'sample_fmts' to value 's32p|fltp|s16p'
[audio format for output stream 0:1 @ 0x9efa7c0] Setting 'sample_rates' to value '22050'
[audio format for output stream 0:1 @ 0x9efa7c0] Setting 'channel_layouts' to value '0x4|0x3'
[audio format for output stream 0:1 @ 0x9efa7c0] auto-inserting filter 'auto-inserted resampler 0' between the filter 'Parsed_anull_0' and the filter 'audio format for output stream 0:1'
[AVFilterGraph @ 0x9f15980] query_formats: 4 queried, 9 merged, 3 already done, 0 delayed
[auto-inserted resampler 0 @ 0x9dfada0] ch:1 chl:mono fmt:s16 r:8000Hz -> ch:1 chl:mono fmt:s16p r:22050Hz
Output #0, flv, to '/dev/null':
  Metadata:
    title           : h264.mp4
    encoder         : Lavf55.12.100
    Stream #0:0, 0, 1/1000: Video: h264 ([7][0][0][0] / 0x0007), yuv420p, 640x480, 1/90000, q=2-31, 1k tbn, 90k tbc
    Stream #0:1, 0, 1/1000: Audio: mp3 (libmp3lame) ([2][0][0][0] / 0x0002), 22050 Hz, mono, s16p
Stream mapping:
  Stream #0:0 -> #0:0 (copy)
  Stream #0:1 -> #0:1 (pcm_mulaw -> libmp3lame)
Press [q] to stop, [?] for help
Current profile doesn't provide more RBSP data in PPS, skippingrate= 135.4kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 134.4kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 135.0kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 135.5kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 136.9kbits/s
Queue input is backward in time=     233kB time=00:00:13.69 bitrate= 139.4kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 136.3kbits/s
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 13926; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 13952; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 13979; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14005; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14031; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14057; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14083; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14109; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14135; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14161; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14188; changing to 14239. This may result in incorrect timestamps in the output file.
[flv @ 0x9de1200] Non-monotonous DTS in output stream 0:1; previous: 14239, current: 14214; changing to 14239. This may result in incorrect timestamps in the output file.
Current profile doesn't provide more RBSP data in PPS, skippingrate= 141.5kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 142.0kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 142.5kbits/s
Receiver Report delay: 469789, gettime: -1527669086, last_recep: 322446, timebase: -1534837492
Current profile doesn't provide more RBSP data in PPS, skippingrate= 141.5kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 141.7kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 141.1kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 140.6kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 140.7kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.9kbits/s
Receiver Report delay: 132993, gettime: -1516538925, last_recep: 322446, timebase: -1518568234
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.6kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.6kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.7kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.4kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 140.0kbits/s
Receiver Report delay: 897727, gettime: -1504870331, last_recep: 322446, timebase: -1518568552
[NULL @ 0x9d9f400] Current profile doesn't provide more RBSP data in PPS, skipping
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.4kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.1kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.0kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 139.0kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 138.6kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 138.5kbits/s
Current profile doesn't provide more RBSP data in PPS, skippingrate= 138.2kbits/s
EOF on sink link output stream 0:1:default.time=00:00:58.40 bitrate= 139.6kbits/s
No more output streams to write to, finishing.
[libmp3lame @ 0x9dfa580] Trying to remove 344 more samples than there are in the queue
frame=  589 fps= 11 q=-1.0 Lsize=    1003kB time=00:00:58.85 bitrate= 139.5kbits/s
video:724kB audio:231kB subtitle:0 global headers:0kB muxing overhead 4.955356%
2959 frames successfully decoded, 0 decoding errors
[AVIOContext @ 0x9e021c0] Statistics: 3 seeks, 2860 writeouts
[root@localhost ffmpeg]#
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1 Answer 1

And... I think I found it. Fun being able to do this as a full-time job. I'm running some tests now, but I'm definately over the one minute threshhold I was working with earlier (by a lot - I'm up to an hour 45 minutes as I type this):

In libavformat/rtpdec.c, function ff_rtp_check_and_send_back_rr, there's a line that says "rtcp_bytes /= 50;" - that number seems to control how often it sends the receiver report. Lowering it makes it happen more often.

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