On 08/08/2011 07:18 PM, Ronald S. Bultje wrote:

> Hi,
> 
> On Sun, Aug 7, 2011 at 4:28 PM, Justin Ruggles <[email protected]> 
> wrote:
>> ---
>>  libavcodec/ac3enc.c          |   10 ++++----
>>  libavcodec/ac3enc.h          |    2 +-
>>  libavcodec/ac3enc_template.c |   50 
>> ++++++++++++++++--------------------------
>>  libavcodec/eac3enc.c         |    2 +-
>>  4 files changed, 26 insertions(+), 38 deletions(-)
> 
> In general, looks OK.
> 
> Something that'd help me (as a future patch, doesn't need to be part
> of this one right away since issue already exists) is if you could
> document what the values 0, 1 and 2 for new_cpl_coords[] means. 0
> means "no channel coupling", 1 means "ac3 uses channel coupling", and
> 2 has something to do with eac3 (default channel coordinates or so?),
> but I'm not quite sure what.


Sorry, yeah I should've done that before.

It is possible to determine the first block in a channel in which to
send coupling coordinates without it being explicitly encoded in the
bitstream, so the spec has a "first coupling coordinates" state variable
for each channel to avoid sending the extra bits.  The 2 is to indicate
that new coordinates need to be sent for the block but don't write the
"send new coordinates" bit to the bitstream.  I'll send a patch to
document that.

-Justin
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