Hi Jianfeng, On Wednesday, June 19, 2024 1:46:23 P.M. EDT Jianfeng Liu wrote: > Hi Detlev, > > On Wed, 19 Jun 2024 10:57:19 -0400, Detlev Casanova wrote: > >+ if (!(sps->flags & V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY)) > >+ height *= 2; > >+ > >+ if (width > ctx->coded_fmt.fmt.pix_mp.width || > >+ height > ctx->coded_fmt.fmt.pix_mp.height) > >+ return -EINVAL; > > I did further invesatigation on chromium. I find that before real video > is decoded, chromium will call VIDIOC_STREAMON twice with value of > sps->flags 0: > > At the first time width and height are 16; ctx->coded_fmt.fmt.pix_mp.width > and coded_fmt.fmt.pix_mp.height are 16, which are the min size of decoder; > At the second time width and height are still 16; while > coded_fmt.fmt.pix_mp.width is 1920 and coded_fmt.fmt.pix_mp.height is > 1088, which are the real size of video. > > So VIDIOC_STREAMON will fall at the first time call because sps->flags is > 0 so V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY is not set, and then height is > doubled to 32 which is larger than 16. > > What do you think if we skip doubling height if sps->flags is 0 and at the > same time V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY is not set? The following hack > did fix my chromium: > > --- a/drivers/staging/media/rkvdec2/rkvdec2-h264.c > +++ b/drivers/staging/media/rkvdec2/rkvdec2-h264.c > @@ -767,7 +767,7 @@ static int rkvdec2_h264_validate_sps(struct rkvdec2_ctx > *ctx, * which is half the final height (see (7-18) in the > * specification) > */ > - if (!(sps->flags & V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY)) > + if (!(sps->flags & V4L2_H264_SPS_FLAG_FRAME_MBS_ONLY) && sps->flags) > height *= 2; > > if (width > ctx->coded_fmt.fmt.pix_mp.width || I'm not sure what Chromium is trying to do here. But the spec is clear that height should be multiplied by 2 (That's actually 7-8, not 7-18): FrameHeightInMbs = ( 2 – frame_mbs_only_flag ) * PicHeightInMapUnits This feels like hacking the driver to please a specific userspace application, so I'd like to understand better what chromium is doing. Regards, Detlev.
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