[FFmpeg-devel] [PATCH, v4] lavc/vp9: fix reference frame dimensions check for SINGLE_REFERENCE mode

[Fu, Linjie]

> From: Ronald S. Bultje <rsbultje at gmail.com>
> Sent: Thursday, March 19, 2020 20:10
> To: FFmpeg development discussions and patches <ffmpeg-devel at ffmpeg.org>
> Cc: Fu, Linjie <linjie.fu at intel.com>
> Subject: Re: [FFmpeg-devel] [PATCH, v4] lavc/vp9: fix reference frame dimensions check for SINGLE_REFERENCE mode
>
> Hi,
>
> On Tue, Mar 17, 2020 at 10:59 AM Linjie Fu <linjie.fu at intel.com<mailto:linjie.fu at intel.com>> wrote:
> With the description in frame size with refs semantics (SPEC 7.2.5),
> it is a requirement of bitstream conformance that for at least one
> reference frame has the valid dimensions.
>
> Modify the check to make sure the decoder works well in SINGLE_REFERENCE
> mode that not all reference frames have valid dimensions.
>
> Check and error out if invalid reference frame is used in inter_recon.
>
> One of the failure case is a 480x272 inter frame (SINGLE_REFERENCE mode)
> with following reference pool:
>
> 0.  960x544    LAST    valid
> 1. 1920x1088 GOLDEN  invalid, but not used in single reference mode
> 2. 1920x1088 ALTREF  invalid, but not used in single reference mode
> 3~7  ...     Unused
>
> Identical logic in libvpx:
> <https://github.com/webmproject/libvpx/blob/master/vp9/decoder/vp9_decodeframe.c#L736>
>
> Signed-off-by: Linjie Fu <linjie.fu at intel.com<mailto:linjie.fu at intel.com>>
> ---
> [v3]: replace assert with check/return, tested in both multi frame/slice mode
> [v4]: clear error_info to make decoding still work for other frames in this stream
>
> libavcodec/vp9.c      | 20 ++++++++++++++++++--
> libavcodec/vp9dec.h   |  5 +++++
> libavcodec/vp9recon.c | 10 ++++++++++
> 3 files changed, 33 insertions(+), 2 deletions(-)
>
> LGTM, thanks for the revisions. (We have been discussing this on IRC.)

Thanks for the review and valuable suggestions.

-  Linjie