user18244: 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 and never displays any frame:
[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 after the streaming is started.
Any help is appreciated.

user18244: It turns out it is impossible to live stream with the RPi hardware acceleration using ffmpeg.
For ffmpeg to configure the hardware acceleration to issue SPS/PPS frames during the stream and not only at the beginning of it, it needs to use a specific API of the raspberry firmware which it does not at the moment. 
Raspivid and gstreamer does that though. So turn to thoses solution and forget about ffmpeg.

18244: <p>Trying to stream a webcam through rtp with a raspberry pi.</p>

<p>Cating the SDP file on my desktop, and launching ffplay:</p>

<pre><code>ffplay sdp.out
</code></pre>

<p>then streaming out this way:</p>

<pre><code>ffmpeg -i /dev/video0 -c:v h264_omx -f rtp rtp://192.168.0.101:1234
</code></pre>

<p>works perfectly. But If I launch ffmpeg first THEN ffplay, ffplay stutters some error message about missing PPS and never displays any frame:</p>

<pre><code>[h264 @ 0x7fd97c0008c0] decode_slice_header error
[h264 @ 0x7fd97c0008c0] no frame!
[h264 @ 0x7fd97c0008c0] non-existing PPS 0 referenced
</code></pre>

<p>After looking for a while I understand some intermediary frame might be missing. However, using the <code>-g</code> option this way does not change anything:</p>

<pre><code>ffmpeg -i /dev/video0 -c:v h264_omx -g 30 -f rtp rtp://192.168.0.101:1234
</code></pre>

<p>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 after the streaming is started.</p>

<p>Any help is appreciated.</p>
 18244: <p>It turns out it is impossible to live stream with the RPi hardware acceleration using ffmpeg.
For ffmpeg to configure the hardware acceleration to issue SPS/PPS frames during the stream and not only at the beginning of it, it needs to use a <a href="https://github.com/raspberrypi/firmware/issues/242" rel="nofollow noreferrer">specific API of the raspberry firmware</a> which it does not at the moment. </p>

<p><a href="http://frozen.ca/streaming-raw-h-264-from-a-raspberry-pi/" rel="nofollow noreferrer">Raspivid</a> and <a href="http://gstreamer-devel.966125.n4.nabble.com/omxh264enc-and-stream-format-string-avc-td4671543.html" rel="nofollow noreferrer">gstreamer</a> does that though. So turn to thoses solution and forget about ffmpeg.</p>
