[FFmpeg-devel] [PATCH] dts probe

[Michael Niedermayer]

On Sat, May 03, 2008 at 01:59:31AM +0200, Benjamin Larsson wrote:
> Michael Niedermayer wrote:
> > 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.
> 
> Will AVPROBE_SCORE_MAX/8 work ?

now you overdo it in the other direction :)
try AVPROBE_SCORE_MAX/2+1 like mpeg-ES

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

I count him braver who overcomes his desires than him who conquers his
enemies for the hardest victory is over self. -- Aristotle
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