[Ffmpeg-devel] [RFC] ZMBV encoder

[Måns Rullgård]

Diego Biurrun <diego at biurrun.de> writes:

> On Tue, Dec 05, 2006 at 06:32:50PM +0100, Michael Niedermayer wrote:
>> 
>> On Tue, Dec 05, 2006 at 05:11:35PM +0100, Benjamin Larsson wrote:
>> > Michael Niedermayer skrev:
>> > [..]
>> > 
>> > >>+#ifdef CONFIG_ZLIB
>> > >>+    // Needed if zlib unused or init aborted before deflateInit
>> > >>+    memset(&(c->zstream), 0, sizeof(z_stream));
>> > >>+#else
>> > >>+    av_log(avctx, AV_LOG_ERROR, "Zlib support not compiled.\n");
>> > >>+    return 1;
>> > >>+#endif
>> > >
>> > >hmm maybe the whole file shouldnt be compiled if zlib isnt available
>> > 
>> > Hi, can we get a policy for this? Currently we have both disabled 
>> > compilation and runtime reporting like this.
>> 
>> yes, theres no sense to compile a codec which then cannot work but just
>> says "oops" ...
>
> Agreed.  IMO we should disable codecs that need zlib when zlib is not
> available.

Zlib compression is optional in ZMBV.  Stupidly enough, zlib
compression is enabled or disabled per frame, and there is no global
flag indicating if zlib is needed to decode the stream.  While it does
make sense to support decoding of non-zlib videos when zlib is not
available, there is no way to tell whether a stream is supported
without decoding all the frames.

Whether to fall back to non-zlib frames when encoding without zlib
available is a matter for debate.

-- 
M?ns Rullg?rd
mru at inprovide.com