gst-rtsp-server share v4l2src accross several mounting points

[jean-philippe]

I return to this topic as the pipeline using intervideosink/src drops frames
when running my SoC (i.MX8M Mini).

The app implements an RTSP server and I'm sharing the v4l2src with several
pipelines. 

*Pipeline #1* is OK:  “v4l2src ! vpuenc_h264 ! rtph264pay”

*Pipeline #2* drops frames: 
“v4l2src ! intervideosink channel=c sync=false”
“intervideosrc channel=c ! vpuenc_h264 ! rtph264pay”

About 1/3 of frames are dropped intermittently. The pipeline may run well
for 10 minutes and then drops frames and then recover after a few minutes.

I am wondering if the problem is related to the BufferPool used.

I have noticed that when pipeline #2 starts it prints
“gstv4l2bufferpool.c:794: … Uncertain of not enough buffers, enabling copy
threshold”. This does not happen with pipeline #1.

I have also noticed the differences below in the debug outputs that make me
think the BufferPool used is different. 

Pipeline #1
v4l2bufferpool
gstv4l2bufferpool.c:509:gst_v4l2_buffer_pool_set_config:<v4l2src0:pool:src>
config GstBufferPoolConfig, caps=(GstCaps)"video/x-raw\,\
format\=\(string\)YUY2\,\ width\=\(int\)1920\,\ height\=\(int\)1080\,\
framerate\=\(fraction\)30/1\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\
colorimetry\=\(string\)bt709\,\ interlace-mode\=\(string\)progressive",
size=(uint)4147200, min-buffers=(uint)5, max-buffers=(uint)5,
allocator=(GstAllocator)"\(GstVpuAllocator\)\ vpuallocator0",
params=(GstAllocationParams)NULL, options=(string)<
GstBufferPoolOptionVideoMeta >;

Pipeline #2
v4l2bufferpool
gstv4l2bufferpool.c:509:gst_v4l2_buffer_pool_set_config:<v4l2src0:pool:src>
config GstBufferPoolConfig, caps=(GstCaps)"video/x-raw\,\
format\=\(string\)YUY2\,\ width\=\(int\)1920\,\ height\=\(int\)1080\,\
framerate\=\(fraction\)30/1\,\ pixel-aspect-ratio\=\(fraction\)1/1\,\
colorimetry\=\(string\)bt709\,\ interlace-mode\=\(string\)progressive",
size=(uint)4147200, min-buffers=(uint)4, max-buffers=(uint)4,
allocator=(GstAllocator)"NULL", params=(GstAllocationParams)NULL;

Could this explain the lost frames? If so, is there any way I can specify
the BufferPool that should be used? Reading the doc on Bufferpool, I cannot
see how to specify a specific Bufferpool on a pad before negotiation.

Is using intervideosink/src a 'bad idea'? Are there better elements to use
to share a v4l2src?



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