[FFmpeg-devel] [PATCH 2/2] avcodec: add eac3_core bitstream filter

[Paul B Mahol]

On 3/28/18, James Almer <jamrial at gmail.com> wrote:
> On 3/28/2018 4:00 PM, Paul B Mahol wrote:
>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>> ---
>>  doc/bitstream_filters.texi     |  4 +++
>>  libavcodec/Makefile            |  1 +
>>  libavcodec/bitstream_filters.c |  1 +
>>  libavcodec/eac3_core_bsf.c     | 80
>> ++++++++++++++++++++++++++++++++++++++++++
>>  4 files changed, 86 insertions(+)
>>  create mode 100644 libavcodec/eac3_core_bsf.c
>>
>> diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
>> index 982e3edac8..7322af6550 100644
>> --- a/doc/bitstream_filters.texi
>> +++ b/doc/bitstream_filters.texi
>> @@ -75,6 +75,10 @@ the header stored in extradata to the key packets:
>>  ffmpeg -i INPUT -map 0 -flags:v +global_header -c:v libx264 -bsf:v
>> dump_extra out.ts
>>  @end example
>>
>> + at section eac3_core
>> +
>> +Extract the core from a E-AC-3 stream, dropping extra channels.
>> +
>>  @section extract_extradata
>>
>>  Extract the in-band extradata.
>> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
>> index aaef6c3ab8..8220ad855d 100644
>> --- a/libavcodec/Makefile
>> +++ b/libavcodec/Makefile
>> @@ -1041,6 +1041,7 @@ OBJS-$(CONFIG_AAC_ADTSTOASC_BSF)          +=
>> aac_adtstoasc_bsf.o mpeg4audio.o
>>  OBJS-$(CONFIG_CHOMP_BSF)                  += chomp_bsf.o
>>  OBJS-$(CONFIG_DUMP_EXTRADATA_BSF)         += dump_extradata_bsf.o
>>  OBJS-$(CONFIG_DCA_CORE_BSF)               += dca_core_bsf.o
>> +OBJS-$(CONFIG_EAC3_CORE_BSF)              += eac3_core_bsf.o
>>  OBJS-$(CONFIG_EXTRACT_EXTRADATA_BSF)      += extract_extradata_bsf.o    \
>>                                               h2645_parse.o
>>  OBJS-$(CONFIG_FILTER_UNITS_BSF)           += filter_units_bsf.o
>> diff --git a/libavcodec/bitstream_filters.c
>> b/libavcodec/bitstream_filters.c
>> index 12211225bb..18b698a85f 100644
>> --- a/libavcodec/bitstream_filters.c
>> +++ b/libavcodec/bitstream_filters.c
>> @@ -28,6 +28,7 @@ extern const AVBitStreamFilter ff_aac_adtstoasc_bsf;
>>  extern const AVBitStreamFilter ff_chomp_bsf;
>>  extern const AVBitStreamFilter ff_dump_extradata_bsf;
>>  extern const AVBitStreamFilter ff_dca_core_bsf;
>> +extern const AVBitStreamFilter ff_eac3_core_bsf;
>>  extern const AVBitStreamFilter ff_extract_extradata_bsf;
>>  extern const AVBitStreamFilter ff_filter_units_bsf;
>>  extern const AVBitStreamFilter ff_h264_metadata_bsf;
>> diff --git a/libavcodec/eac3_core_bsf.c b/libavcodec/eac3_core_bsf.c
>> new file mode 100644
>> index 0000000000..85feb2583b
>> --- /dev/null
>> +++ b/libavcodec/eac3_core_bsf.c
>> @@ -0,0 +1,80 @@
>> +/*
>> + * Copyright (c) 2018 Paul B Mahol
>> + *
>> + * This file is part of FFmpeg.
>> + *
>> + * FFmpeg is free software; you can redistribute it and/or
>> + * modify it under the terms of the GNU Lesser General Public
>> + * License as published by the Free Software Foundation; either
>> + * version 2.1 of the License, or (at your option) any later version.
>> + *
>> + * FFmpeg is distributed in the hope that it will be useful,
>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>> + * Lesser General Public License for more details.
>> + *
>> + * You should have received a copy of the GNU Lesser General Public
>> + * License along with FFmpeg; if not, write to the Free Software
>> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
>> 02110-1301 USA
>> + */
>> +
>> +#include "avcodec.h"
>> +#include "bsf.h"
>> +#include "get_bits.h"
>> +#include "libavutil/mem.h"
>
> Why?
>
>> +#include "ac3_parser_internal.h"
>> +
>> +static int eac3_core_filter(AVBSFContext *ctx, AVPacket *pkt)
>> +{
>> +    AC3HeaderInfo hdr;
>> +    GetBitContext gbc;
>> +    int ret;
>> +
>> +    ret = ff_bsf_get_packet_ref(ctx, pkt);
>> +    if (ret < 0)
>> +        return ret;
>> +    ret = init_get_bits8(&gbc, pkt->data, pkt->size);
>> +    if (ret < 0)
>> +        return ret;
>
> av_packet_unref(pkt);
>
> Same with every other failure below, so maybe doing a goto fail would be
> easier.
>
>> +
>> +    ret = ff_ac3_parse_header(&gbc, &hdr);
>> +    if (ret < 0)
>> +        return AVERROR_INVALIDDATA;
>> +
>> +    if (hdr.frame_type == EAC3_FRAME_TYPE_INDEPENDENT ||
>> +        hdr.frame_type == EAC3_FRAME_TYPE_AC3_CONVERT) {
>> +        pkt->size = hdr.frame_size;
>> +    } else if (hdr.frame_type == EAC3_FRAME_TYPE_DEPENDENT && pkt->size >
>> hdr.frame_size) {
>> +        AC3HeaderInfo hdr2;
>> +
>> +        ret = init_get_bits8(&gbc, pkt->data + hdr.frame_size, pkt->size
>> - hdr.frame_size);
>> +        if (ret < 0)
>> +            return ret;
>> +
>> +        ret = ff_ac3_parse_header(&gbc, &hdr2);
>> +        if (ret < 0)
>> +            return AVERROR_INVALIDDATA;
>> +
>> +        if (hdr2.frame_type == EAC3_FRAME_TYPE_INDEPENDENT ||
>> +            hdr2.frame_type == EAC3_FRAME_TYPE_AC3_CONVERT) {
>> +            pkt->size -= hdr.frame_size;
>> +            pkt->data += hdr.frame_size;
>> +        } else {
>> +            pkt->size = 0;
>> +        }
>> +    } else {
>> +        pkt->size = 0;
>> +    }
>> +
>> +    return 0;
>> +}
>> +
>> +static const enum AVCodecID codec_ids[] = {
>> +    AV_CODEC_ID_EAC3, AV_CODEC_ID_NONE,
>> +};
>> +
>> +const AVBitStreamFilter ff_eac3_core_bsf = {
>> +    .name      = "eac3_core",
>> +    .filter    = eac3_core_filter,
>> +    .codec_ids = codec_ids,
>> +};
>>
>

All done.