Adding support for DSDIFF

[Bart Lauret]

Hello Scott c.s.,

With the possible upcoming rise of the usage of the DSDIFF format
(.DFF extension), I wanted to add support for it to taglib. This
fileformat contains DSD audio (1-bit audio used on SACDs) in an AIFF
(EA-IFF 85)-like container. The most used ripping software for these
DSDIFFs (sacd-ripper) creates an ID3 chunk (but it is not part of the
official spec).

The specs of DSDIFF can be found here:
http://www.sonicstudio.com/pdf/dsd/DSDIFF_1.5_Spec.pdf

Trying to get this to work I have encountered two problems while using
the RIFF class with DFF.
- It is not completely compatible to the RIFF class, because it uses 8
bytes for the size of the chunk. From the DSDIFF spec: "[T]he
ckDataSize is not 4 bytes in length, as in EA-IFF 85, but 8 bytes.
This makes it possible to create chunks larger than 2 GigaByte (up to
2^64 bytes)."

- Next problem is that the RIFF class only reads chunks which are
sub-chunks of the main chunk. As the ID3 chunk in DFF is a
sub-sub-chunk ('FRM8'->'PROP'->'ID3 '), it is not processed.
Furthermore, all the interesting audio-property information (channel
count, compression type, timestamp, loudspeaker configuration) are
also in the PROP chunk.

So, does this together warrant a move away from the RIFF class, or
should the RIFF class be changed to cope with this? Also, are you
interested in official support for DSDIFF?

Regards,
Bart Lauret