[FFmpeg-devel] [PATCh] aac parser: Don't write channels, sample rate, and frame size each frame

[Alex Converse]

On Wed, Mar 3, 2010 at 5:12 AM, Michael Niedermayer <michaelni at gmx.at> wrote:
> On Wed, Mar 03, 2010 at 05:06:32AM -0500, Alex Converse wrote:
>> On Mon, Mar 1, 2010 at 8:23 PM, Michael Niedermayer <michaelni at gmx.at> wrote:
>> > On Mon, Mar 01, 2010 at 08:16:48PM -0500, Alex Converse wrote:
>> >> They are part of the invariant header and shouldn't change each frame
>> >> anyway. This prevents them from overwriting information provided by
>> >> backwards compatible extensions.
>> >
>> > what you attached does not match the description
>> >
>> > besides "shouldn't change" gives me a strange feeling ...
>> > if we can support it changing it would be a nice "wish/feature request"
>> >
>>
>> This patch appears to be necessary for either the put a hack in
>> av_find_stream_info() or fix all the demuxers approach to handling
>> backwards compatible SBR. It breaks nothing we already support as far
>> as I can tell.
>>
>> Based on that should we move forward with it, make some changes to it,
>> or try to move to a new approach?
>>
>> [patch re-attched]
>>
>> --Alex
>
>> ?aac_ac3_parser.c | ? 10 +++++++---
>> ?1 file changed, 7 insertions(+), 3 deletions(-)
>> 074f9a540038b4836308ca477b806204f56c6229 ?aac_parser_extensions.diff
>> diff --git a/libavcodec/aac_ac3_parser.c b/libavcodec/aac_ac3_parser.c
>> index 85993c0..23a1d0a 100644
>> --- a/libavcodec/aac_ac3_parser.c
>> +++ b/libavcodec/aac_ac3_parser.c
>> @@ -71,10 +71,12 @@ get_next:
>> ? ? ?*poutbuf_size = buf_size;
>>
>> ? ? ?/* update codec info */
>> - ? ?avctx->sample_rate = s->sample_rate;
>> ? ? ?if(s->codec_id)
>> ? ? ? ? ?avctx->codec_id = s->codec_id;
>>
>> + ? ?if (avctx->codec_id != CODEC_ID_AAC) {
>> + ? ? ? ?avctx->sample_rate = s->sample_rate;
>> +
>
> this one needs a comment, its likely not obvious for the causual reader why
> this is not done for aac
>

fixed

>
>> ? ? ?/* allow downmixing to stereo (or mono for AC-3) */
>> ? ? ?if(avctx->request_channels > 0 &&
>> ? ? ? ? ? ? ?avctx->request_channels < s->channels &&
>> @@ -83,12 +85,14 @@ get_next:
>> ? ? ? ? ? ? ?(avctx->codec_id == CODEC_ID_AC3 ||
>> ? ? ? ? ? ? ? avctx->codec_id == CODEC_ID_EAC3)))) {
>> ? ? ? ? ?avctx->channels = avctx->request_channels;
>> - ? ?} else if (avctx->codec_id != CODEC_ID_AAC || s->channels) {
>> + ? ?} else {
>> ? ? ? ? ?avctx->channels = s->channels;
>> ? ? ? ? ?avctx->channel_layout = s->channel_layout;
>> ? ? ?}
>> - ? ?avctx->bit_rate = s->bit_rate;
>> ? ? ?avctx->frame_size = s->samples;
>> + ? ?}
>
> id guess this could benefit from a comment as well
>

what do you mean by "this"? bit rate?

Revised patch attached.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: aac_parser_extensions.diff
Type: text/x-patch
Size: 1413 bytes
Desc: not available
URL: <http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/attachments/20100303/2a380fb9/attachment.bin>