[FFmpeg-devel] [PATCH] dts probe

[Benjamin Larsson]

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 ?

And I will fix the for loop bug in the commit.

MvH
Benjamin Larsson