v4l2h264dec Raspberry PI

Nicolas Dufresne nicolas at ndufresne.ca
Sat May 18 13:14:53 UTC 2019

Le sam. 18 mai 2019 05 h 10, horai <ivo.hora at seznam.cz> a écrit :

> If it is not correct, just give me a hint and I will do what is necessary.
> Anyway, I rebuild gstreamer-plugin-base as well as gtreamer-plugin-good
> with
> kernel header of 4.19.* in the system. Now it was compiled with dma-buf.h
> included and the following message is gone:
> gstdmabuf.c:93:gst_dmabuf_mem_unmap:<dmabufallocator2> Using DMABuf without
> synchronization.
> Anyway, the following warning is still present:
> pi at raspberrypi:~ $ ./playFile
> Setting pipeline to PAUSED ...
> 0:00:01.449266020 23614  0x1feda80 WARN                 basesrc
> gstbasesrc.c:3600:gst_base_src_start_complete:<filesrc0> pad not activated
> yet
> Pipeline is PREROLLING ...
> 0:00:01.457391198 23614  0x1de5320 WARN                    v4l2
> gstv4l2object.c:4194:gst_v4l2_object_probe_caps:<v4l2h264dec0:src> Failed
> to
> probe pixel aspect ratio with VIDIOC_CROPCAP: Invalid argument

This one can be ignored. It's really minor, the driver should have returned
ENOTTY instead of EINVAL, but the outcome is the same. This is normally to
read back the pixel aspect ratio, but the video parsers does that for us

0:00:01.468336190 23614  0x1de5320 WARN            v4l2videodec
> gstv4l2videodec.c:810:gst_v4l2_video_dec_decide_allocation:<v4l2h264dec0>
> Duration invalid, not setting latency

This one should be fixed, should be info, and should say that framerate is
not set (duration is calculated from it).

0:00:01.477499274 23614  0x1de5320 WARN          v4l2bufferpool
> gstv4l2bufferpool.c:807:gst_v4l2_buffer_pool_start:<v4l2h264dec0:pool:src>
> Uncertain or not enough buffers, enabling copy threshold
> 0:00:01.508788331 23614 0x6f313830 WARN          v4l2bufferpool
> gstv4l2bufferpool.c:1263:gst_v4l2_buffer_pool_dqbuf:<v4l2h264dec0:pool:src>
> Driver should never set v4l2_buffer.field to ANY

That one means that clutter sink didn't fully replied to the allocation
query. This warning is valid, because you may end up with a image copies,
that would cause jitter. Clutter sink is a bit unmaintained.

What I'm thinking now is that you're options are limited on the PI at the
moment. I'd try and get glimagesink working, and would use GstVideoOverlay
to embed it in your application. To check if dmabuf upload is working, use
the following log level:


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