MJPEG support

[MichaelAronsen]

Hi,

Not sure this should be an issue, but rather a question.

But since v4l2 device in the pi now has mjpeg support, would it be possible to simply stream the raw mjpeg stream from v4l2 over rtsp using v4l2rtspserver?

Reason I ask is that mjpeg would allow for higher resolution and less compression.

Regards,
Michael

[mpromonet]

Hi,

This works, but the bandwidth is much higher.
I don't undersand why do you think jpeg capture allow higher resolution, the compression is done after capture.

Regards,
Michel.

[MichaelAronsen]

It allows higher resolution as there is some limit in the pi GPU code that
limits h264 to max 1920x1080, where as mjpeg is not limited.

See this post:
http://www.lewisroberts.com/2015/05/15/raspberry-pi-mjpeg-at-30fps/

[MichaelAronsen]

How would I enable mjpeg streaming rather than h264?

[mpromonet]

using -fJPEG

[prechtl]

I am trying to implement this mjpeg encoding as well. I have taken the basic instructions and made the following changes:

I set the original uv4l command using:
sudo uv4l --driver raspicam --auto-video_nr --encoding mjpeg

Then as you suggest, I call the server w/ the -fJPEG option using
./v4l2rtspserver -s -fJPEG

However, when I include the '-fJPEG' option and open my VLC terminal to view the rtsp://:8554/unicast stream, my VLC window just jumps back and forth between two sizes - but no video shows up. Whereas if I eliminate the '-fJPEG' option I get video to show up. Problem is that when I view the 'Codec information' in VLC for this video, it ID's the Codec as: 'H264 - MPEG-4 AVC (part 10) (h264)' So it's unclear to me that this is using mjpeg encoding ... seems tied to H264.

(fyi: I'm interested in avoiding H264 b/c of the parallel question I have asked in this github project where I'm trying to capture full field-of-view video that uses all 2592 x 1944 pixels of the raspberry pi camera)

[mpromonet]

Hi prechtl,

If you are using uv4l (that is closed source), I guess you should use --encoding jpeg. Generaly I prefer to use the official V4L2 driver bcm2835-v4l2

Using -s option is probably a bad idea, it will read from the V4L2 capture device and send to network in the same thread.

An other point is the RFC2435 encode width and height dividing by 8 and storing as 8bit. Then the maximum is 2040x2040.

But there is many others problem... trying with vlc I got the problem you describe, and with ffplay the size is the half of the capture one.

Regards,
Michel.

[prechtl]

I agree - there seem to be many problems. I installed the uv4l drivers hoping it would help - but uv4l seems to add a lot of additional resources.

Can you provide an example command to generate video w/ v4l2 (using 'v4l2-ctl' specifiers, I guess?). For example, to generate video with vlc, you can use a command:
cvlc --no-audio v4l2:///dev/video0 --v4l2-width 1920 --v4l2-height 1440 --v4l2-chroma MJPG

What is the equivalent command that is compatible with your v4l2rtspserver code (using -fJPEG)?

(I am assuming here that your rtsp server takes the place of vlc in transmitting the video data?)