VPUDEC I420 output frame structure

erez1 — Sun, 05 May 2019 19:31:56 GMT

We are currently building this GStreamer pipline:

appsrc ! "video/x-h264, width=(int)1024, height=(int)768, framerate=(fraction)0/1, stream-format=(string)avc" ! queue max-size-time=0 ! vpudec output-fotmat=2 ! "video/x-raw,(string)format=I420, width=(int)1024, height=(int)768" ! queue ! appsink

In the appsink CB we try to isolate the Y, U, V byte-streams and the strides.

According to the I420 specification, for NxM frame we should get:

Y - first NxM bytes

U - next NxM/4 bytes

V - last NxM/4 bytes.

So for 1024x768 we should get a frame of 1179648 bytes, however we actually get a fame of 1376288 bytes, and we are unable to really get the correct Y,U,V offsets and sizes.

As far we understand, the format we are using (I420) is 14.1.3.1 which should be 12 bits per pixel.

While the frame that we get from the voudec is not so clear how many bits per pixel is used.

For a 1024x768 with 12 bpp we are expecting a 1179648 bytes frame, while we get from the vpudec 1376288.

This difference make it almost impossible to correctly parse the frame.

Can you please detail the vpudec's I420 output frame structure (offsets,sizes, strides)?

Re: VPUDEC I420 output frame structure

joanxie — Wed, 08 May 2019 08:55:12 GMT

pls test it on the unit test first, the path is unit_tests/V4L2_VPU/mxc_v4l2_vpu_dec.out, if you don't know how to set the parameter, try to use mxc_v4l2_vpu_dec.out -help

i.MX ProcessorsのトピックVPUDEC I420 output frame structure

VPUDEC I420 output frame structure

Re: VPUDEC I420 output frame structure