how does v4l2display_h264 work?

[WiredLife]

i tried v4l2display_h264 -vv -W 480 -H 320 -F 15 /dev/video1 hoping that shows me the video on framebuffer and display, but it dont it only says waiting

[WiredLife]

v4l2grab_h264 : grab raspberry pi screen, compress in H264 format using OMX and write to a V4L2 output device

v4l2display_h264 : read H264 from V4L2 capture device, uncompress and display using OMX

I need to display the video1 raw h264 on my display

I've run a v4l2rtspserver that shares video0 and clone to video1 (v4l2loopback)

[mpromonet]

Hi,

v4l2display_h264 read H264 frames from a V4L2 device and display using OMX.

In order to works, it is important that the V4L2 device repeat the SPS/PPS. It just makes somehow what does ffplay /dev/video1 with many less feature, and only with an H264 data.

Best Regards, Michel.

[WiredLife]

@mpromonet

i'm broadcasting the video from raspberry cam (video0) to rtsp and want the direct video on my 3,5" spi tft which reads framebuffer so i did that

modprobe v4l2loopback devices=5 v4l2rtspserver -O /dev/video1 -H 1232 -W 1640 -F 15 -P 8555 /dev/video0

and now i want to display but this dont work v4l2display_h264 -vv -W 480 -H 320 -F 15 /dev/video1 gives only waiting... first packet waiting... waiting... and so on...

v4l2-ctl --all -d /dev/video1 gives me this Driver Info: Driver name : v4l2 loopback Card type : Dummy video device (0x0000) Bus info : platform:v4l2loopback-000 Driver version : 4.19.75 Capabilities : 0x85208003 Video Capture Video Output Video Memory-to-Memory Read/Write Streaming Extended Pix Format Device Capabilities Device Caps : 0x85208003 Video Capture Video Output Video Memory-to-Memory Read/Write Streaming Extended Pix Format Device Capabilities Priority: 0 Video input : 0 (loopback: ok) Video output: 0 (loopback in) Format Video Capture: Width/Height : 1640/1232 Pixel Format : 'H264' (H.264) Field : None Bytes per Line : 0 Size Image : 8081920 Colorspace : sRGB Transfer Function : Default (maps to sRGB) YCbCr/HSV Encoding: Default (maps to ITU-R 601) Quantization : Default (maps to Full Range) Flags : Format Video Output: Width/Height : 1640/1232 Pixel Format : 'H264' (H.264) Field : None Bytes per Line : 0 Size Image : 8081920 Colorspace : sRGB Transfer Function : Default (maps to sRGB) YCbCr/HSV Encoding: Default (maps to ITU-R 601) Quantization : Default (maps to Full Range) Flags : Streaming Parameters Video Capture: Frames per second: 15.000 (15/1) Read buffers : 8 Streaming Parameters Video Output: Frames per second: 15.000 (15/1) Write buffers : 8

User Controls

                keep_format 0x0098f900 (bool)   : default=0 value=0
          sustain_framerate 0x0098f901 (bool)   : default=0 value=0
                    timeout 0x0098f902 (int)    : min=0 max=100000 step=1 default=0 value=0
           timeout_image_io 0x0098f903 (bool)   : default=0 value=0

[mpromonet]

@WiredLife,

The OMX will not be display on the framebuffer, in order to copy screen to framebuffer you could look at https://github.com/tasanakorn/rpi-fbcp or get the decoded frame and write to the framebuffer.

Best Regards,

Michel.

[aweussom]

@WiredLife,

The OMX will not be display on the framebuffer, in order to copy screen to framebuffer you could look at https://github.com/tasanakorn/rpi-fbcp or get the decoded frame and write to the framebuffer.

If it is a chinese SPI display clone, neither v4l2display_h264 or rpi-fbcp will work? ffplay should, though. Or OMXplayer, perhaps.

For my setup, I streamed rtsp to the PI browser.

[WiredLife]

@mpromonet @aweussom i'm using fbcp-ili9341 driver which copy fb0 to fb1 i can see video with cvlc -vvv rtsp://127.0.0.1:8555/unicast --network-caching=0 --fbdev=/dev/fb0 but this sucks because of delay and sometimes pixelating opening video1 does not work, maybe there is something missing?

i need to view video1 directly

edit: mplayer says this Error while decoding frame! [h264 @ 0xb5d9b118]non-existing PPS 0 referenced [h264 @ 0xb5d9b118]decode_slice_header error [h264 @ 0xb5d9b118]no frame!

i dont know much about that maybe this is not working? v4l2rtspserver -O /dev/video1 -H 1232 -W 1640 -F 15 -P 8555 /dev/video0

[WiredLife]

i've found a solution by @mpromonet after some google v4l2-ctl -c repeat_sequence_header=1 and then i can do v4l2display_h264 -vv -W 480 -H 320 -F 15 /dev/video1 this gives me 30% disturbed picture in the lower so i'm using cvlc -vvv v4l2:///dev/video1 --noaudio --fbdev=/dev/fb0 which works fine

maybe someone knows the parameter to disable buffering? want near 0ms delay

[mpromonet]

Hi @WiredLife

Yes in my first answer it is pointed out that SPS/PPS should be present, otherwise v4l2display_h264 or vlc cannot decode the H264 stream.

There is no buffering in v4l2display_h264 and a very small in v4l2rtspserver that is control by the parameter -Q.

Best Regards, Michel.

[WiredLife]

Great its working with nearly no delay!

v4l2rtspserver -O /dev/video1 -Q 1 -H 1232 -W 1640 -F 15 -P 8555 /dev/video0 cvlc -vvv v4l2:///dev/video1 --live-caching=150 --file-caching=5 --sout-mux-caching=5 --noaudio --fbdev=/dev/fb0

150ms is the lowest value, under that its missing frames and becomes delayed too

[mpromonet]

Hi,

I think below -Q3 could brings some problem. In my experiment reading from V4L2 an H264 stream give in a same call SPS/PPS/IDR, that will be splitted in 3 frames to the queue (because each one is send in a different RTP packet). This will work for the copy to loopback but it might cause problem for RTP streaming ?

vlc seems an heavy solution to decode the stream and copy it to framebuffer, using OMX to decode the stream and writing to the framebuffer may be not so complex ?

Best Regards, Michel.

[WiredLife]

vlc is yet the only solution that works v4l2display_h264 has still disturbed image mplayer and ffmpeg dont show any image on framebuffer here

[WiredLife]

are there any news on get this working without pixelated image? i'm runinng v4l2rtspserver -O /dev/video1 -Q 3 -H 1232 -W 1640 -F 15 -P 8555 /dev/video0,dsnoopedmic -C 1; done and v4l2display_h264 /dev/video1 but the image is still pixelating

[mpromonet]

Hi @WiredLife

Did you check your H264 source, it may be also pixelated ? (For example using v4l2display_h264 /dev/video0, without rtsp stremaner) I just made a test, and I don't see pixelization, it depends on configuration of the v4L2 device.

Best Regards, Michel