GStreamer - Webcam stream from Raspberry to VLC-PC

Question

I'm trying to stream webcam video from a Raspberry to a VLC player using gstreamer 1.0. Right now i got the following command for the Raspberry:

gst-launch-1.0 -vv -e v4l2src device=/dev/video0  \
! videoscale \
! "video/x-raw,width=352,height=288,framerate=10/1" \
! queue  \
! x264enc \
! h264parse \
! rtph264pay config-interval=10 pt=96 \
! udpsink host=239.255.12.42 port=5004

And the following sdp file to play the stream with vlc:

c=IN IP4 239.255.12.42
m=video 5004 RTP/AVP 96
a=rtpmap:96 H264/90000

When i run the gst-launch-1.0 command i can see with wireshark that it is sending udp packets but when i try to play the stream with vlc and the sdp file i get nothing. The vlc log says:

es error: cannot peek
es error: cannot peek
live555 error: no data received in 10s, aborting

I don't know what's wrong. I probably have'nt build the pipeline properly and that's why the vlc does not recognize the stream as a proper video stream. Any ideas?

Thanks in advance for your help.

Thanks for your reply @otopolsky. I tried and yes, now it shows some images... but it's incredibly slow. The vlc log says main error: ES_OUT_SET_(GROUP_)PCR is called too late (pts_delay increased to 567 ms) main error: ES_OUT_RESET_PCR called avcodec error: more than 5 seconds of late video -> dropping frame (computer too slow ?). Maybe h264 it's too much for the raspberry. I'm trying to find an encoder that doesn't need that much horsepower from the raspberry. So far, no luck. — DaveCode
what about setting faster preset on x264enc? try speed-preset=2 or you can try even tune=zerolatency — nayana
Hi again @otopolsky! I tried and same result... vlc log says: es error: cannot peek es error: cannot peek main error: Failed to resize display avcodec error: more than 5 seconds of late video -> dropping frame (computer too slow ?) avcodec error: more than 5 seconds of late video -> dropping frame (computer too slow ?).I'll have to keep searching :). Thanks for the reply! — DaveCode
what happens when you just use in vlc rtp://@:5004 ? you can also try without scale, it may be too much for rpi.. what is the CPU load when you do that? — nayana

nayana nayana · Accepted Answer · 2016-02-02T08:57:14

VLC understand ts stream combined with RTP protocol. The approach is to use rtp payloader after mpegtsmux which will payload the generated ts buffers (packets).

So instead of this:

src ! queue ! x264enc ! h264parse ! rtph264pay ! udpsink

You can do this:

src ! queue ! x264enc ! h264parse ! mpegtsmux ! rtpmp2tpay ! udpsink

And then use just rtp://@:port in vlc In this way the mpegtsmux will encapsulate information about what streams does it contains

I should note that your approach is not incorrect, and could be even more effective (mpegtsmux will slice video into 188 Byte packets, but your approach will slice into ~ 1400 Bytes udp packets), but you need to provide correct SDP file for vlc in order to stream it. For example like this but I do not have much experience with this..

So this is your current pipe which works:

gst-launch-1.0 -vv -e v4l2src device=/dev/video0 ! "video/x-raw,width=352,height=288,framerate=25/1"\ ! queue ! x264enc speed-preset=1 ! h264parse ! mpegtsmux ! rtpmp2tpay ! udpsink host=192.255.10.41 port=5004

You can maybe achieve better results when using zerolatency:

like this x264enc tune=4 it will discard all other quality parameters like speed-preset etc..

This is from docs about tune property:

tune : Preset name for non-psychovisual tuning options
       flags: readable, writable
       Flags "GstX264EncTune" Default: 0x00000000, "(none)"
       (0x00000001): stillimage       - Still image
       (0x00000002): fastdecode       - Fast decode
       (0x00000004): zerolatency      - Zero latency

GStreamer - Webcam stream from Raspberry to VLC-PC

1 Answers