[FFmpeg-devel] [PATCH] avformat/westwood_aud: Adds PCM format demux.

[Michael Niedermayer]

On Wed, Feb 27, 2019 at 11:12:08PM +0000, Aidan R wrote:
> PCM format AUD files are found in Westwood's Blade Runner game.
> ---
>  libavformat/westwood_aud.c | 80 ++++++++++++++++++++++++++++++++++++----------
>  1 file changed, 63 insertions(+), 17 deletions(-)
> 
> diff --git a/libavformat/westwood_aud.c b/libavformat/westwood_aud.c
> index 9c2d35cb8a..5d7e827bc1 100644
> --- a/libavformat/westwood_aud.c
> +++ b/libavformat/westwood_aud.c
> @@ -41,6 +41,12 @@
>  #define AUD_HEADER_SIZE 12
>  #define AUD_CHUNK_PREAMBLE_SIZE 8
>  #define AUD_CHUNK_SIGNATURE 0x0000DEAF
> +#define AUD_PCM_CHUNK_SIZE 2048 /* arbitrary size to pull out of PCM data*/
> +
> +typedef struct AUDDemuxContext {
> +    int size;
> +    int pos;
> +} AUDDemuxContext;
>  
>  static int wsaud_probe(AVProbeData *p)
>  {
> @@ -50,10 +56,10 @@ static int wsaud_probe(AVProbeData *p)
>       * so perform sanity checks on various header parameters:
>       *   8000 <= sample rate (16 bits) <= 48000  ==> 40001 acceptable numbers
>       *   flags <= 0x03 (2 LSBs are used)         ==> 4 acceptable numbers
> -     *   compression type (8 bits) = 1 or 99     ==> 2 acceptable numbers
> +     *   compression type (8 bits) = 0, 1 or 99  ==> 3 acceptable numbers
>       *   first audio chunk signature (32 bits)   ==> 1 acceptable number
> -     * The number space contains 2^64 numbers. There are 40001 * 4 * 2 * 1 =
> -     * 320008 acceptable number combinations.
> +     * The number space contains 2^64 numbers. There are 40001 * 4 * 3 * 1 =
> +     * 480012 acceptable number combinations.
>       */
>  
>      if (p->buf_size < AUD_HEADER_SIZE + AUD_CHUNK_PREAMBLE_SIZE)
> @@ -69,13 +75,22 @@ static int wsaud_probe(AVProbeData *p)
>      if (p->buf[10] & 0xFC)
>          return 0;
>  
> -    if (p->buf[11] != 99 && p->buf[11] != 1)
> +    /* valid format values are 99 == adpcm, 1 == snd1 and 0 == pcm */
> +    if (p->buf[11] != 99 && p->buf[11] != 1 && p->buf[11] != 0)
>          return 0;
>  
> -    /* read ahead to the first audio chunk and validate the first header signature */
> -    if (AV_RL32(&p->buf[16]) != AUD_CHUNK_SIGNATURE)
> +    /* read ahead to the first audio chunk and validate the first header
> +     * signature pcm format does not use a chunk format, so don't check
> +     * for that codec */
> +    if (p->buf[11] != 0 && AV_RL32(&p->buf[16]) != AUD_CHUNK_SIGNATURE)
>          return 0;
>  
> +    /* if we have pcm format then compressed size should equal
> +     * uncompressed size */
> +    if (p->buf[11] == 0 && AV_RL32(&p->buf[2]) != AV_RL32(&p->buf[6]))  {
> +        return 0;
> +    }
> +
>      /* return 1/2 certainty since this file check is a little sketchy */
>      return AVPROBE_SCORE_EXTENSION;
>  }

this seems to break probetest
tools/probetest 256 1024
testing size=1
testing size=2
testing size=4
testing size=8
testing size=16
testing size=32
Failure of wsaud probing code with score=50 type=0 p=EBC size=32
testing size=64
testing size=128
testing size=256
testing size=512

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Freedom in capitalist society always remains about the same as it was in
ancient Greek republics: Freedom for slave owners. -- Vladimir Lenin
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