[FFmpeg-devel] [PATCH] Set CODEC_CAP_SUBFRAMES for adpcm decoders

[Måns Rullgård]

Michael Niedermayer <michaelni at gmx.at> writes:

> On Thu, Jan 21, 2010 at 04:42:27PM +0000, M?ns Rullg?rd wrote:
>> Michael Niedermayer <michaelni at gmx.at> writes:
>> 
>> > On Thu, Jan 21, 2010 at 02:12:26PM +0000, M?ns Rullg?rd wrote:
>> >> Benjamin Larsson <banan at ludd.ltu.se> writes:
>> >> 
>> >> > M?ns Rullg?rd wrote:
>> >> >> I thought adpcm was one of those non-byte-aligned codecs, at least
>> >> >> some variants.
>> >> >
>> >> > It is.
>> >> 
>> >> Which means frame-splitting is not generally possible.
>> >
>> > ADPCM in general comes in frames with a header of an initial sample
>> > and a series of adaptive delta coded fixed length (generally
>> > 4 bit) symbols
>> > but there are exceptions. The general case though certainly can be split
>> 
>> General in this context means something that is always true.  If there
>> exist adpcm streams with non-byte-aligned frames, they cannot be split
>> in the general case, which includes these streams.
>> 
>> It may be that in the _majority_ of streams can be split, but unless
>> there's an easy way to determine this without actually trying it, I
>> don't think we should be requiring it.
>
> We have 27 adpcm decoders, some of them can be split into frames, some
> do not know a concept of frames != packets some maybe cannot be split.
> They all use an AVCodec struct build out of a macro to which you added
> the flag, thus effectively adding it to 27 different codecs, some of
> which are not even capable of returning subframes no matter what is in
> the bitstream.

If someone tells me which of decoders need the flag I will fix it.

-- 
M?ns Rullg?rd
mans at mansr.com