Return to Basic Components of a SV8 stream.

Detect components:

Read two octets and then lookup in the following table:

Range	Possible meaning
0000...1FFF	Length Label
0000...0001	impossible
0002...1FFF	possible
2000...3FFF	Cutted SV8 Audioframe
2000...31FE	possible
31FF...3FFF	impossible
3FFF...7FFF	Tags, Sync Labels, Header
4150	APE Tag 2.0
4944	ID3 Version 2.x Tag
4D50	SV7 / SV8 Header
5441	ID3 Version 1.x Tag
664B	Transport Streaming Synchronization Label
8000...FFDF	raw SV8 Audio frame
FFE0...FFFF	MPEG Layer 1, 2 or 3 Frame
FFE0...FFE7	MPEG 2.5
FFF0...FFF7	MPEG 2
FFF7...FFFF	MPEG 1

This only showns what may be possible. There're additional restriction which can be used to check validy of the component.

Determine size of components:

Resynchronization of Interchange File Format:

• Search for byte b1 of the format 000x xxxx
• Byte at offset -2 from that also should have the format 000x xxxx. Exception is the first frame.
• Read next byte b2. The same pattern must occure at offset (256 * b1 + b2 + 2) far from that.
• Byte at offset (256 * b1 + b2 + 4) from that also should have the format 000x xxxx. Exception is the last frame.
• You can do that multiple times.
• You can also decode a frame and test the decoded size against the sync label size.

    uint8_t*  p;                                        // Pointer to data stream
    uint16_t  len_pre;
    uint16_t  len_post;

repeat:
    while ( (p[0] & 0xE0)  ||  (p[2] & 0xE0) )          // search for two length labels (p=1.5%)
        p++;

    len_pre  = p[2]           * 256 + p[3];             // decode pre and post length label
    len_post = p[4 + len_pre] * 256 + p[5 + len_pre];

    if ( len_pre != len_post ) {                        // they should be the same, otherwise continue with next byte (p=2ppm)
        p++;
        goto repeat;
    }
    if ( p[6 + len_pre] & 0xE0 ) {                      // after the post length label the pre length label of the next frame (p=0.24ppm)
        p++;                                            // should be available
        goto repeat;
    }
    if ( determine_len (p+4) != len_pre ) {             // test length of stream contents against length labels (p<1ppb)
        p++;
        goto repeat;
    }
    p += 4;
    // p points to the start of a raw audio frame