[vlc-devel] VLC with VDPAU is falling back to s/w decoding for vc1 simple profile clips.

Rémi Denis-Courmont remi at remlab.net
Wed Feb 20 14:16:26 CET 2019

Ignoring levels is obviously not safe. That's why VLC does not use that flag.

Le 20 février 2019 13:07:42 GMT+02:00, Manoj Bonda <mbonda at nvidia.com> a écrit :
>VLC with VDPAU is falling back to s/w decoding for vc1 simple and Main
>profile clips.
>i.e. with cmd ./vlc --avcodec-hw=vdpau
>and error is reported as, "Failed setup for format vdpau: hwaccel
>initialisation returned error"
>This failure is due to level check in function ff_vdpau_common_init()
>in ffmpeg/libavcodec/vdpau.c
>The level is not populated in ffmpeg for vc1 simple and main profile
>As the level will be communicated via transport layer, as per section
>D.4 Syntax (Informative) from vc1 spec
>"The Simple and Main profiles are communicated to the decoder by the
>syntax element PROFILE as part of the
>initialization metadata as described in Annex J.1.1. The Advanced
>profile is signaled to the decoder in the bitstream,
>by the syntax element PROFILE, which is included in the sequence header
>as described in Section 6.1.1.
>The levels for Simple and Main profile are to be communicated to the
>decoder by the Transport Layer. The levels for
>Advanced profile are indicated in the syntax element LEVEL, which is
>included in the sequence header, as described in Section 6.1.2.
>The following codes are used to signal the levels in this profile:"
>I see, ffmpeg sets 'AV_HWACCEL_FLAG_IGNORE_LEVEL' flag. Hence, the
>level is initialized to zero
>while using ffmpeg. This lets standalone ffmpeg application and Mplayer
>to decode the clip with VDPAU hw acceleration.
>I observed that VLC is not setting AV_HWACCEL_FLAG_IGNORE_LEVEL flag,
>level gets initialized to -99,
>and eventually fails the check in ff_vdpau_common_init() resulting in
>the failure reported above.
>Attaching the patch for setting AV_HWACCEL_FLAG_IGNORE_LEVEL flag in
>VLC as well.
>I am curious what others think about this issue.
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