[FFmpeg-devel] [PATCH] dts probe

[Benjamin Larsson]

Michael Niedermayer wrote:
> 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
> 

Committed, and now how do I use this to probe dts in wav files? I never
understood the logic.

MvH
Benjamin Larsson