[FFmpeg-devel] [PATCH] Add a parser for DNET (byte-swapped AC3).

Anssi Hannula anssi.hannula
Thu Mar 3 01:27:56 CET 2011

On 03.03.2011 00:18, M?ns Rullg?rd wrote:
> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>> On Wed, Mar 02, 2011 at 09:10:21PM +0000, M?ns Rullg?rd wrote:
>>> Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
>>>>> Then how did you intend to detect it as ac3 in the first place?
>>>> By the fact that the RealMedia header says "DNET"?
>>> AC3 exists outside of realmedia file, you know...
>> So what? Has anyone seen the byte-swapped variant outside a container?
>> Either way libavformat has a better infrastructure to do this kind
>> of format detection when it's hard to decide, a parser is not really
>> such a great place for it.
> The parser can reasonably assume it is being fed AC3 data in some form
> or other, so the difficulty of detection is irrelevant there.
>> Which, as said, is in addition to the fact whether there is a point
>> at all of supporting byte-swapped raw AC3. It obviously exists
>> in other containers, but already for that there seem to be no samples
>> available, DNET is the only one actually common (and even that seems
>> relative).
> AC3 in WAV is fairly common.  I'm sure we have a few samples of that.

Note that our spdif/iec61937 demuxer already does the byteswap for that
case, so the decoder doesn't need to handle it.

(note that I'm not for or against anything, just making sure all the
facts are available :) )

> All else aside, calling it DNET is ridiculous.  It is called AC3
> whatever container you wrap it in.  We don't have a CODEC_ID_ for every
> tag used in some obscure container, we have one per codec.  Please keep
> it that way.

Anssi Hannula

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