I did a little more digging.
This, on my Desktop, works (meaning, I can start ffplay AFTER ffmpeg):
ffmpeg -i /dev/video0 -force_key_frames 'expr:gte(t,n_forced)' -c:v libx264
-f rtp rtp://127.0.0.1:1234
This, on my RPi, does not (meaning, I can NOT start ffplay after ffmpeg):
ffmpeg -i /dev/video0 -force_key_frames 'expr:gte(t,n_forced)' -c:v
h264_omx -f rtp rtp://192.168.0.101:1234
So there must be some problem with the hardware encoder h264_omx...
Any help is appreciated.
________________________________
De : ffmpeg-user <ffmpeg-user-boun...@ffmpeg.org> de la part de luke
<skywa...@hotmail.com>
Envoyé : vendredi 3 mars 2017 18:00
À : FFmpeg user questions
Objet : Re: [FFmpeg-user] h264_omx and non-existing PPS 0 referenced
To clarify, ffplay does display any image, it just keep outputting the error
message regarding missing PPS.
I had a look and someone mentioned -force_key_frames on video.stackexchange.com.
I tried this:
./ffmpeg -i /dev/video0 -c:v h264_omx -force_key_frames
'expr:gte(t,n_forced)' -f rtp rtp://192.168.0.101:1234
But ffplay is still not able to display anything if not started first.
If I dump the output into a file, I see that intermediate frames are generated:
./ffmpeg -i /dev/video0 -c:v h264_omx -force_key_frames
'expr:gte(t,n_forced)' -o file.avi
./ffprobe -i file.avi -select_streams v -show_frames -of csv -show_entries
frame=pict_type
frame,I
frame,P
frame,P
frame,P
frame,P
frame,P
frame,P
frame,P
frame,P
frame,P
frame,P
frame,P
frame,I
frame,P
frame,P
frame,P
[...]
So why would ffplay not able to decode those frame? Is this a limitation of the
rdp protocol somehow.
________________________________
De : ffmpeg-user <ffmpeg-user-boun...@ffmpeg.org> de la part de luke
<skywa...@hotmail.com>
Envoyé : jeudi 2 mars 2017 19:17
À : ffmpeg-user@ffmpeg.org
Objet : [FFmpeg-user] h264_omx and non-existing PPS 0 referenced
Trying to stream a webcam through rtp with a raspberry pi.
Cating the SDP file on my desktop, and launching ffplay:
ffplay sdp.out
then streaming out this way:
ffmpeg -i /dev/video0 -c:v h264_omx -f rtp rtp://192.168.0.101:1234
works perfectly. But If I launch ffmpeg first THEN ffplay, ffplay stutters some
error message about missing PPS:
[h264 @ 0x7fd97c0008c0] decode_slice_header error
[h264 @ 0x7fd97c0008c0] no frame!
[h264 @ 0x7fd97c0008c0] non-existing PPS 0 referenced
After looking for a while I understand some intermediary frame might be
missing. However, using the -g option this way does not change anything:
ffmpeg -i /dev/video0 -c:v h264_omx -g 30 -f rtp rtp://192.168.0.101:1234
It is a problem for me because I am using the raspberry as a securiy camera. My
desktop can be restarted from time to time and I need ffplay to be able to
catch long after streaming is started.
Any help is appreciated.
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