[FFmpeg-devel] [PATCH v4] lavf/matroskadec: Normalize noncompliant A_QUICKTIME/V_QUICKTIME private data

[Michael Niedermayer]

On Sat, Jan 09, 2016 at 12:02:19PM +0100, Mats Peterson wrote:
> Minor simplification of get_qt_codec(). Description follows:
> 
> This patch adds a new static function get_qt_codec() that takes care
> of the initial retrieval of the fourcc and codec ID for A_QUICKTIME
> and V_QUICKTIME. It also normalizes noncompliant private data found
> in some older files that incorrectly starts with the fourcc by
> expanding/shifting the data by 4 bytes, and storing the data size at
> the start. This is necessary in order for the rest of the code in
> the A_QUICKTIME and V_QUICKTIME blocks (and most likely other code
> as well) to correctly parse the private data.
> 
> Mats
> 
> -- 
> Mats Peterson
> http://matsp888.no-ip.org/~mats/

>  matroskadec.c |   47 ++++++++++++++++++++++++++++++++++-------------
>  1 file changed, 34 insertions(+), 13 deletions(-)
> 714309bb2cd9614cb58dfdaa5c05574d53386bb5  0001-lavf-matroskadec-Normalize-noncompliant-A_QUICKTIME-.patch
> From 9448cff9c5cdd1e301da8868c8e2e189ef34c760 Mon Sep 17 00:00:00 2001
> From: Mats Peterson <matsp888 at yahoo.com>
> Date: Sat, 9 Jan 2016 11:59:18 +0100
> Subject: [PATCH v4] lavf/matroskadec: Normalize noncompliant A_QUICKTIME/V_QUICKTIME private data
> 
> Minor simplification of get_qt_codec(). Description follows:
> 
> This patch adds a new static function get_qt_codec() that takes care of
> the initial retrieval of the fourcc and codec ID for A_QUICKTIME and
> V_QUICKTIME. It also normalizes noncompliant private data found in some
> older files that incorrectly starts with the fourcc by expanding/shifting
> the data by 4 bytes, and storing the data size at the start. This is
> necessary in order for the rest of the code in the A_QUICKTIME and
> V_QUICKTIME blocks (and most likely other code as well) to correctly
> parse the private data.
> 
> Mats
> 
> ---
>  libavformat/matroskadec.c |   47 ++++++++++++++++++++++++++++++++-------------
>  1 file changed, 34 insertions(+), 13 deletions(-)
> 
> diff --git a/libavformat/matroskadec.c b/libavformat/matroskadec.c
> index be4e300..71bf5e5 100644
> --- a/libavformat/matroskadec.c
> +++ b/libavformat/matroskadec.c
> @@ -1708,6 +1708,32 @@ static void mkv_stereo_mode_display_mul(int stereo_mode, int *h_width, int *h_he
>      }
>  }
>  
> +static int get_qt_codec(MatroskaTrack *track, uint32_t *fourcc, enum AVCodecID *codec_id)
> +{
> +    const AVCodecTag *codec_tags;
> +    
> +    codec_tags = track->type == MATROSKA_TRACK_TYPE_VIDEO ?
> +            ff_codec_movvideo_tags : ff_codec_movaudio_tags;
> +
> +    /* Normalize noncompliant private data that starts with the fourcc
> +     * by expanding/shifting the data by 4 bytes and storing the data
> +     * size at the start. */
> +    if (ff_codec_get_id(codec_tags, AV_RL32(track->codec_priv.data))) {

> +        if (!(track->codec_priv.data = av_realloc(track->codec_priv.data,
> +                track->codec_priv.size + 4)))
> +            return AVERROR(ENOMEM);

in case of this failing the memory is not freed and leaks

see av_reallocp() if you want it to be freed, alternatively the code
could continue without the move/update

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Complexity theory is the science of finding the exact solution to an
approximation. Benchmarking OTOH is finding an approximation of the exact
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