[Ffmpeg-devel] Contacting developers by subversion name
Fri Dec 29 20:47:39 CET 2006
Apologies for the top post.
On 29/12/06, M?ns Rullg?rd <mru at inprovide.com> wrote:
> Don't top-post.
> "Paul Richards" <paul.richards at gmail.com> writes:
> > On 29/12/06, M?ns Rullg?rd <mru at inprovide.com> wrote:
> >> "Paul Richards" <paul.richards at gmail.com> writes:
> >> > Hi,
> >> > Apologies for spamming the mailing list. Is there an easy way to
> >> > contact a developer given their subversion name?
> >> >
> >> > I am attempting to implement an output codec, and I am using other
> >> > codecs for reference (in this case oggvorbis.c). I am currently
> >> > looking to contact "mru", or anyone familiar with oggvorbis.c.
> >> That would be me, but I'm afraid I'm no more familiar with oggvorbis.c
> >> than anyone. I didn't write it, and I'm not the maintainer of it.
> >> Just say what you need to know, and we'll probably try to tell you.
> > I'm looking from line 104 onwards. At this part the various
> > ogg_packet structs are being packed together into the AVCodecContext's
> > extradata fields. There is some magic happening that I don't follow:
> > len = header.bytes + header_comm.bytes + header_code.bytes;
> > avccontext->extradata_size= 64 + len + len/255;
> > p = avccontext->extradata= av_mallocz(avccontext->extradata_size);
> > p = 2;
> > offset = 1;
> > offset += av_xiphlacing(&p[offset], header.bytes);
> > offset += av_xiphlacing(&p[offset], header_comm.bytes);
> > memcpy(&p[offset], header.packet, header.bytes);
> > offset += header.bytes;
> > memcpy(&p[offset], header_comm.packet, header_comm.bytes);
> > offset += header_comm.bytes;
> > memcpy(&p[offset], header_code.packet, header_code.bytes);
> > offset += header_code.bytes;
> > avccontext->extradata_size = offset;
> > avccontext->extradata= av_realloc(avccontext->extradata,
> > avccontext->extradata_size);
> > Can the "64 + len + len / 255" expression be explained? I see that
> > the buffer is later reduced in size based on the actual value for
> > offset. Is this expression simply something which is guessed to be
> > "large enough"?
> That's right.
> > Can the "p = 2" be explained?
> The first byte is followed by 2 xiph-coded values.
> > What does av_xiphlacing do? It has no documentation that I can find.
> It has source code.
> Do yourself a favor and keep away from the xiph brain damage. What
> are you trying to accomplish?
I am trying to use libtheora inside libavcodec to add theora encoding
to ffmpeg. I'm making progress again now. The ffmpeg / theora
mailing lists and irc channels are very helpful. :)
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