[FFmpeg-devel] [PATCH] Matroska Muxer

Michael Niedermayer michaelni
Fri Aug 24 12:45:03 CEST 2007


On Thu, Aug 23, 2007 at 08:47:24PM -0400, David Conrad wrote:
> On Aug 20, 2007, at 4:30 PM, David Conrad wrote:
>> On Aug 14, 2007, at 3:13 PM, Michael Niedermayer wrote:
>>> Hi
>>> On Mon, Aug 13, 2007 at 08:38:25PM -0400, David Conrad wrote:
>>>> +}
>>>> +
>>>> +/**
>>>> + * Calculate how many bytes are needed to represent a given size in 
>>>> EBML
>>>> + */
>>>> +static int ebml_size_bytes(uint64_t size)
>>>> +{
>>>> +    int bytes = 1;
>>>> +    while ((size+1) >> bytes*7) bytes++;
>>>> +    return bytes;
>>>> +}
>>> isnt ebml_size_bytes and ebml_id_size the same if the IDs would be stored
>>> properly?
>>> i mean currently the #define *_ID_* is in encoded form while size of 
>>> course
>>> cannot be, so if we would change the #defines to be in normal form then i
>>> think this could allow some simplifications, though i might be wrong ...
>> I think this is possible, the only caveat is that if IDs with all ones are 
>> ever used (they're currently reserved) then this won't work for them. I'll 
>> send a patch changing the demuxer, then change the muxer.
> Another thing I realized is that I'm pretty sure that an ID of 0x81 is 
> considered different from an ID of 0x4001, but they're the same number if 
> not in ebml form. I don't think there are any IDs right now that this is an 
> issue for.
> Another problem is that the IDs are stored in encoded form in the seek head 
> as unsigned integers (thus they need to be read by ebml_read_uint(), and 
> they're compared to the #defines. I can't come up with a clean way to 
> handle that in matroska_parse_seekhead() that doesn't completely negate the 
> simplification to the muxer.
> Attached is the current difference for doing this for the muxer and 
> demuxer, comments?

aurelian? are you ok with this, if not iam fine with leaving the code as
is and use the normal #defines in the muxer  ...

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

When you are offended at any man's fault, turn to yourself and study your
own failings. Then you will forget your anger. -- Epictetus
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