[vlc-devel] [PATCH] modules/demux/mkv/matroska_segment_parse.cpp: fix hvcC detection with mkvmerge

[Steve Lhomme]

Le 21/02/2018 à 14:50, Alexandre Janniaux a écrit :
> mkvmerge had an issue with the first reserved bits and fixed it in v16.0.0
> in the commit 4bb8ad6f5565e87ad6d6a8e7e9d453e64985344e. Some files done
> with anterior versions were not played by VLC with mediacodec.
> See the changelog of mkvmerge for version 16.0.0, especially the
> following:
> * mkvmerge: HEVC/h.265: the generation of the HEVCC structure stored in
>    `CodecPrivate` was wrong in two places: 1. the position of the number of
>    sub-layers was swapped with reserved bits and 2. the VPS/SPS/PPS/SEI lists
>    did not start with a reserved 1 bit.
> See also https://code.videolan.org/videolan/vlc-android/issues/466 for issue
> and sample.
> ---
>   modules/demux/mkv/matroska_segment_parse.cpp | 19 +++++++++++++++++++
>   1 file changed, 19 insertions(+)
>
> diff --git a/modules/demux/mkv/matroska_segment_parse.cpp b/modules/demux/mkv/matroska_segment_parse.cpp
> index 0b82866bb7..af55f4d7b8 100644
> --- a/modules/demux/mkv/matroska_segment_parse.cpp
> +++ b/modules/demux/mkv/matroska_segment_parse.cpp
> @@ -1587,6 +1587,25 @@ bool matroska_segment_c::TrackInit( mkv_track_t * p_tk )
>           }
>           S_CASE("V_MPEGH/ISO/HEVC") {
>               vars.p_tk->fmt.i_codec = VLC_CODEC_HEVC;
> +
> +            uint8_t* p_extra = (uint8_t*) vars.p_tk->p_extra_data;
> +
> +            /* HACK: if we found invalid format, made by mkvmerge < 16.0.0,
> +             *       we try to fix it. They fixed it in 16.0.0. */
> +            const char* app = vars.obj->psz_writing_application;
> +            if( app != NULL && strncmp(app, "mkvmerge", strlen("mkvmerge")) == 0
> +                    && p_extra && p_extra[0] == 0 )

You may put the p_extra checks before the (more expensive) strncmp() call.
Other than that LGTM

> +            {
> +                int major_version;
> +                if( sscanf(app, "mkvmerge v%d.", &major_version) && major_version < 16 )
> +                {
> +                    msg_Dbg(vars.p_demuxer,
> +                            "Invalid HEVC reserved bits in mkv file"
> +                            "made by mkvmerge < v16.0.0 detected, fixing it");
> +                    p_extra[0] = 0x01;
> +                }
> +            }
> +
>               fill_extra_data( vars.p_tk, 0 );
>           }
>           S_CASE("V_QUICKTIME") {