Le 24/09/2017 à 5:06 PM, Rostislav Pehlivanov a écrit :
On 24 September 2017 at 15:27, pkv.stream <pkv.str...@gmail.com> wrote:
Hi atomnuker and others
I am interested in working on this patch by atomnuker who did a great job.
This could allow encoding to more channels with aac (e.g. ambisonics order
three = 16 audio channels).
Here's a report about additions I made to the PCE table for all the basic
ffmpeg channel layouts (except mixed stereo).
I have followed atomnuker assumptions for the guess work, notably
regarding indexes (which seems right, I saw on spec an example with indexes
running like 0 1 0 so ithe indexing seems to reset , quite probably for
each group of either, front, side, back or LFE channels in the PCE).
I have done some testing:
encoding goes without fuss up to 16 channels. No warning, no error.
But, ffmpeg aac decoder is throwing errors in aacdec_template.c :
lines 3119-3124:
if (elem_type < TYPE_DSE) {
if (!(che=get_che(ac, elem_type, elem_id))) {
av_log(ac->avctx, AV_LOG_ERROR, "channel element %d.%d is
not allocated\n",
elem_type, elem_id);
err = AVERROR_INVALIDDATA;
goto fail;
error message is:
channel element 0.0 is not allocated
So the get_che function is failing.
Of course it isn't going to work, I explicitly told you 1.) its a wip patch
so no real error reporting and 2.) you need to add a new entry for whatever
messed up channel layout ambisonics use and make sure the signalling
indices are correct. And the latter isn't easy since nothing tells you
what's correct - the spec, a decoder or anything like that.
I understand.
I did get though a decode of pce 4.0 or quad with vlc (downmixed to
stereo by my sound card). In contrast ffmpeg aac decoder throws the
error I mentioned (in ffmpeg and ffplay).
So already your pce code is not doing a bad job.
My point is maybe faad2 is perhaps implementing pce decode better than
ffmpeg own aac decoder.
Or your pce implementation might miss something that faad2 works around.
I'll inquire and post if I find something useful for getting functional
pce.
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