[MPlayer-dev-eng] MPCF: sub_packet_size concerns

[Michael Niedermayer]

Hi

On Friday 14 February 2003 15:52, D Richard Felker III wrote:
> On Fri, Feb 14, 2003 at 12:13:17PM +0100, Michael Niedermayer wrote:
> > Hi
> >
> > On Friday 14 February 2003 07:12, D Richard Felker III wrote:
> > > Michael, I was just reading thru mpcf.txt again, and I'm a bit
> > > confused about how the sub_packet_size field is supposed to work. Are
> > > you assuming audio will always be multiple fixed-size packets per
> > > container-level packet? This is definitely not the case for vorbis,
> > > which uses variable size packets, so if our new container can only
> > > handle fixed-sized audio packets, it's mostly useless, since the
> > > immediate use would be to mux vorbis audio with mpeg4.
> > >
> > > If this isn't a problem, the document at least needs to specify how
> > > variable-length audio packets should be stored. Somehow storing a
> > > whole mpcf packet for each audio packet (several hundred bytes) seems
> > > really wasteful. Do you have something in mind to handle this better?
> >
> > ok fixed, i am no audio expert and i didnt think much about the subpacket
> > stuff and missed that its not able to handle variable length subpackets
> > :(((
>
> What about in addition to storing subpacket_size_diff[], also storing
> subpacket_length_diff[] for decoded lengths. That would make subpacket
> seeking possible, solving one of the main idiocies of ogg format. IMHO
> we don't want to repeat the brain damage of ogg where you can only
> seek to page boundaries!! One of the main points of mpcf was to allow
> arbitrary seeking in audio files.
hmm, i dont remember that point on the goals list ...
anyway isnt the number of samples per packet constant ? if not then we need to 
think about this a bit

some possible solutions:
1. limit the maximum length (in time) of a packet so that precisse enough 
seeking is possible
2. add a optional timestamp or number of samples to the subpackets
3. decode a whole packet and drop the samples until the point to which we want 
to seek

[...]

Michael