[FFmpeg-devel] [PATCH 3/4] lavc/aac_ac3_parser: convert ADTS AAC to ASC format

[Hendrik Leppkes]

On Tue, Sep 22, 2015 at 4:50 AM, Rodger Combs <rodger.combs at gmail.com> wrote:
> ---
>  libavcodec/aac_ac3_parser.c | 65 ++++++++++++++++++++++++++++++++++++++++++---
>  tests/ref/fate/adts-demux   |  2 +-
>  2 files changed, 63 insertions(+), 4 deletions(-)
>
> diff --git a/libavcodec/aac_ac3_parser.c b/libavcodec/aac_ac3_parser.c
> index dfa951e..a7e9278 100644
> --- a/libavcodec/aac_ac3_parser.c
> +++ b/libavcodec/aac_ac3_parser.c
> @@ -24,6 +24,10 @@
>  #include "libavutil/common.h"
>  #include "parser.h"
>  #include "aac_ac3_parser.h"
> +#include "aacadtsdec.h"
> +#include "put_bits.h"
> +#include "get_bits.h"
> +#include "mpeg4audio.h"
>
>  int ff_aac_ac3_parse(AVCodecParserContext *s1,
>                       AVCodecContext *avctx,
> @@ -69,9 +73,6 @@ get_next:
>          return buf_size;
>      }
>
> -    *poutbuf = buf;
> -    *poutbuf_size = buf_size;
> -
>      /* update codec info */
>      if(s->codec_id)
>          avctx->codec_id = s->codec_id;
> @@ -98,7 +99,65 @@ get_next:
>          }
>          s1->duration = s->samples;
>          avctx->audio_service_type = s->service_type;
> +    } else if (AV_RB16(buf) & 0xfff0 == 0xfff0) {
> +        GetBitContext gb;
> +        AACADTSHeaderInfo hdr;
> +        int            pce_size = 0;
> +        uint8_t        pce_data[MAX_PCE_SIZE];
> +        init_get_bits(&gb, buf, AAC_ADTS_HEADER_SIZE * 8);
> +        if (avpriv_aac_parse_header(&gb, &hdr) < 0) {
> +            av_log(avctx, AV_LOG_ERROR, "Error parsing ADTS frame header!\n");
> +            goto skip_adts;
> +        }
> +        if (!hdr.crc_absent && hdr.num_aac_frames > 1) {
> +            avpriv_report_missing_feature(avctx, "Multiple RDBs per frame with CRC");
> +            goto skip_adts;
> +        }
> +
> +        buf      += AAC_ADTS_HEADER_SIZE + 2 * !hdr.crc_absent;
> +        buf_size -= AAC_ADTS_HEADER_SIZE + 2 * !hdr.crc_absent;
> +
> +        if (!avctx->extradata) {
> +            PutBitContext pb;
> +            if (!hdr.chan_config) {
> +                init_get_bits(&gb, buf, buf_size * 8);
> +                if (get_bits(&gb, 3) != 5) {
> +                    avpriv_report_missing_feature(avctx,
> +                                                  "PCE-based channel configuration "
> +                                                  "without PCE as first syntax "
> +                                                  "element");
> +                    goto skip_adts;
> +                }
> +                init_put_bits(&pb, pce_data, MAX_PCE_SIZE);
> +                pce_size = avpriv_copy_pce_data(&pb, &gb) / 8;
> +                flush_put_bits(&pb);
> +                buf_size -= get_bits_count(&gb) / 8;
> +                buf      += get_bits_count(&gb) / 8;
> +            }
> +            av_free(avctx->extradata);
> +            avctx->extradata_size = 2 + pce_size;
> +            avctx->extradata = av_mallocz(avctx->extradata_size + AV_INPUT_BUFFER_PADDING_SIZE);
> +            if (!avctx->extradata) {
> +                avctx->extradata_size = 0;
> +                goto skip_adts;
> +            }
> +
> +            init_put_bits(&pb, avctx->extradata, avctx->extradata_size);
> +            put_bits(&pb, 5, hdr.object_type);
> +            put_bits(&pb, 4, hdr.sampling_index);
> +            put_bits(&pb, 4, hdr.chan_config);
> +            put_bits(&pb, 1, 0); //frame length - 1024 samples
> +            put_bits(&pb, 1, 0); //does not depend on core coder
> +            put_bits(&pb, 1, 0); //is not extension
> +            flush_put_bits(&pb);
> +            if (pce_size)
> +                memcpy(avctx->extradata + 2, pce_data, pce_size);
> +        }
>      }
> +skip_adts:
> +
> +    *poutbuf = buf;
> +    *poutbuf_size = buf_size;
>
>      avctx->bit_rate = s->bit_rate;
>

This is not acceptable. ADTS has a bunch of advantages, for example,
you can change the stream properties on the fly in a broadcast, which
this would break entirely.