[Vorbis] Byte order in ogg vorbis headers

[Ralph Giles]

On 6-Jul-08, at 12:07 AM, Ryan Rix wrote:

> The issue I seem to be having is that when parsing the comments I  
> use a for loop limited by the number of fields, which is a value  
> stored within the ogg file, one or two bytes before the comments  
> begin (I don't have my code handy to check atm) According to the  
> Vorbis docs this is stored as unsigned integer of 32 bits. I assume  
> that it is x86 little endian and thus byte swap it using
> an OS provided macro.

Yes, the comment count and lengths are stored in little-endian order,  
so either the files are broken or it's another issue with your code.

You can clip the count and comment lengths against the size of the  
packet, which should get rid of the hang even if you fail to retrieve  
the comments.

Otherwise, remember the 32 bit ints aren't necessarily aligned. Make  
sure you take the vendor string's length into account in finding the  
comment count. "A few bytes before the comments start" sounds  
suspiciously like you're not using a full parser, so make sure you've  
got the second packet in the vorbis stream, and note that if the  
comments are more than 4kB, they may not be stored contiguously.

That's all I can suggest without seeing your code. Hope it helps,

  -r