We have been initially working with the 2110 decode example on the github site 
(https://github.com/cbcrc/FFmpeg) and have been successfully streaming media 
with it. We have evolved our design and would like to operate with multiple 
media streams. We have a configuration where we are using gstreamer to stream 
two media files, and we are trying to connect to the audio streams in two 
different instances of ffmpeg. However we are noticing unexpected behavior. I 
was hoping someone could comment on this behavior, and if it is expected, or if 
you have any insight/suggestions as to what might be incorrect in my 
configuration or how I could identify/correct the issue. We have configured the 
ffmpeg instances to use the bshowvolume filter, so that ffplay can display an 
audio gauge for each output. A flow diagram of our experiment is shown below. 
(filenames in paranthesis)


(gst_AUD1)stream 1 --> ffmpeg_instance1 --> ffplay_instance1 (test1.sdp)

(gst_AUD2)stream 2 --> ffmpeg_instance2 --→ffplay_instance2 (test2.sdp)


A script is used to start ffplay/ffmpeg instances (ff_scrpt). The gstreamer 
instances are started one at a time afterward. The results are different based 
on stream order started.

One ffmpeg (via its sdp file) is configured to connect to the higher IP 
addressed stream. The other ffmpeg is configured to connect to the lower IP 
addressed stream. I am trying to stream the audio media only, and connect & 
process the audio only (via the sdp file audio-only media specifications).


The behavior we are seeing is the following:

If the gstreamer with the higher IP address is started first, both ffmpeg 
instances connect with it. Once the gstreamer with the lower IP address is 
started, both ffmpeg instances switch over to it & play to its completion. (the 
ffmpeg-20211201-213419.log file)./

If the gstreamer with the lower IP address is started first, both ffmpeg 
instances connect with it. Once the gstreamer with the higher IP address is 
started, both ffmpeg instances switch over to it, but the ffplay display locks 
up when the first gstreamer stream stops (if it runs shorter than the second 
gstreamer stream). (ffmpeg-20211201-214224.log file)


I was expecting the ffmpeg instances to connect to the multicast address that 
their respective sdp files specified, but it doesn't seem to be working that 
way.


I have attached the log files for the two runs, the ffmpeg script, and the 
gstreamer scripts, and the sdp files. I can send the media files if desired but 
they are large.

I am running in a Ubuntu 20.04.3 LTS environment.


We have additionally tested with later versions of ffmpeg (downloaded from the 
ffmpeg site, not the ST2110 version) and have noted the same behavior. We 
additionally added a filter to the sdp file (added a=source-filter:incl IN IP4 
239.0.0.0 192.168.68.112 after the “c=IN…” line to help with ffmpeg stream 
selection, and o=- 0 0 IN IP4 192.168.68.112 in the session area) and this 
provided no changes in behavior. (originally, the sdp files did not have this 
“a=…” line in them; and 192.168.68.112 is the IP address of the local PC doing 
the testing).


Testing is being performed on 1 PC. Both streams have been verified to be 
present on the test system.


The logs are on a google drive that is shared to everyone using this link:


https://drive.google.com/drive/folders/1xv0bwAxDBWSrA-mJRRov0Oj4njh6ZQNw?usp=sharing



Please let me know if you are able to provide any insight/assistance.

Thank you,

Robert Wood

407-457-9939


Robert E Wood
Engineering
[cid:c5403db5-c876-4c24-ae84-06db04a68c43]
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