[FFmpeg-devel] [PATCH] dts probe

[Michael Niedermayer]

On Sat, May 03, 2008 at 12:42:05AM +0200, Benjamin Larsson wrote:
> $topic
> 
> MvH
> Benjamin Larsson

> Index: libavformat/raw.c
> ===================================================================
> --- libavformat/raw.c	(revision 12892)
> +++ libavformat/raw.c	(working copy)
> @@ -22,6 +22,7 @@
>  #include "avformat.h"
>  #include "ac3_parser.h"
>  #include "raw.h"
> +#include "bytestream.h"
>  
>  #ifdef CONFIG_MUXERS
>  /* simple formats */
> @@ -413,6 +414,40 @@
>      return 0;
>  }
>  
> +
> +#define DCA_MARKER_14B_BE 0x1FFFE800
> +#define DCA_MARKER_14B_LE 0xFF1F00E8
> +#define DCA_MARKER_RAW_BE 0x7FFE8001
> +#define DCA_MARKER_RAW_LE 0xFE7F0180
> +static int dts_probe(AVProbeData *p)
> +{
> +    const uint8_t *buf, *bufp;
> +    uint32_t state = -1;
> +
> +    buf = p->buf;
> +
> +    for(; buf < (buf+p->buf_size)-2; buf+=2) {
> +        bufp = buf;
> +        state = (state << 16) | bytestream_get_be16(&bufp);
> +
> +        /* Regular bitstream */
> +        if (state == DCA_MARKER_RAW_BE || state == DCA_MARKER_RAW_LE)
> +            return AVPROBE_SCORE_MAX;
> +
> +        /* 14 bits big endian bitstream */
> +        if (state == DCA_MARKER_14B_BE)
> +            if ((bytestream_get_be16(&bufp) & 0xFFF0) == 0x07F0)
> +                return AVPROBE_SCORE_MAX;
> +
> +        /* 14 bits little endian bitstream */
> +        if (state == DCA_MARKER_14B_LE)
> +            if ((bytestream_get_be16(&bufp) & 0xF0FF) == 0xF007)
> +                return AVPROBE_SCORE_MAX;
> +    }
> +
> +    return 0;
> +}

AVPROBE_SCORE_MAX is a little big for a single 4 byte marker found at
an arbitrary position.
The score for a single header at arbitrary position must at least be
smaller than mpeg-ps/ts or they will be missdetected. Yeah
dts+mpeg2 in mpeg-ps must be detected as mpeg-ps not dts.

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

The greatest way to live with honor in this world is to be what we pretend
to be. -- Socrates
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