On 3/4/2020 7:26 PM, Paul B Mahol wrote:
> Signed-off-by: Paul B Mahol <one...@gmail.com>
> ---
> libavformat/Makefile | 1 +
> libavformat/ac4dec.c | 104 +++++++++++++++++++++++++++++++++++++++
> libavformat/allformats.c | 1 +
> 3 files changed, 106 insertions(+)
> create mode 100644 libavformat/ac4dec.c
>
> diff --git a/libavformat/Makefile b/libavformat/Makefile
> index e0681058a2..b4e8d20e65 100644
> --- a/libavformat/Makefile
> +++ b/libavformat/Makefile
> @@ -70,6 +70,7 @@ OBJS-$(CONFIG_AA_DEMUXER) += aadec.o
> OBJS-$(CONFIG_AAC_DEMUXER) += aacdec.o apetag.o img2.o rawdec.o
> OBJS-$(CONFIG_AC3_DEMUXER) += ac3dec.o rawdec.o
> OBJS-$(CONFIG_AC3_MUXER) += rawenc.o
> +OBJS-$(CONFIG_AC4_DEMUXER) += ac4dec.o
> OBJS-$(CONFIG_ACM_DEMUXER) += acm.o rawdec.o
> OBJS-$(CONFIG_ACT_DEMUXER) += act.o
> OBJS-$(CONFIG_ADF_DEMUXER) += bintext.o sauce.o
> diff --git a/libavformat/ac4dec.c b/libavformat/ac4dec.c
> new file mode 100644
> index 0000000000..8c6e539409
> --- /dev/null
> +++ b/libavformat/ac4dec.c
> @@ -0,0 +1,104 @@
> +/*
> + * RAW AC-4 demuxer
> + * Copyright (c) 2019 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 "libavutil/avassert.h"
> +#include "libavutil/crc.h"
> +#include "avformat.h"
> +#include "rawdec.h"
> +
> +static int ac4_probe(const AVProbeData *p)
> +{
> + const uint8_t *buf = p->buf;
> + int left = p->buf_size;
> + int max_frames = 0;
> +
> + while (left > 7) {
> + int size;
> +
> + if (buf[0] == 0xAC &&
> + (buf[1] == 0x40 ||
> + buf[1] == 0x41)) {
> + size = (buf[2] << 8) | buf[3];
> + if (size == 0xFFFF)
> + size = 3 + (buf[4] << 16) | (buf[5] << 8) | buf[6];
> + size += 4;
> + if (buf[1] == 0x41)
> + size += 2;
> + max_frames++;
> + left -= size;
> + buf += size;
> + } else {
> + break;
> + }
> + }
> +
> + return FFMIN(AVPROBE_SCORE_MAX, max_frames * 7);
> +}
> +
> +static int ac4_read_header(AVFormatContext *s)
> +{
> + AVStream *st;
> +
> + st = avformat_new_stream(s, NULL);
> + if (!st)
> + return AVERROR(ENOMEM);
> +
> + st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
> + st->codecpar->codec_id = AV_CODEC_ID_AC4;
> +
> + return 0;
> +}
> +
> +static int ac4_read_packet(AVFormatContext *s, AVPacket *pkt)
> +{
> + AVIOContext *pb = s->pb;
> + int64_t pos;
> + uint16_t sync;
> + int ret, size;
> +
> + if (avio_feof(s->pb))
> + return AVERROR_EOF;
> +
> + pos = avio_tell(s->pb);
> + sync = avio_rb16(pb);
If there are sync codes then it sounds like the proper thing to do is,
much like with AC3, writing a trivial parser to assemble frames and then
use ff_raw_audio_read_header() and ff_raw_read_partial_packet() here
instead of custom functions.
> + size = avio_rb16(pb);
> + if (size == 0xffff)
> + size = avio_rb24(pb);
> +
> + ret = av_get_packet(pb, pkt, size);
> + pkt->pos = pos;
> + pkt->stream_index = 0;
> +
> + if (sync == 0xAC41)
> + avio_skip(pb, 2);
> +
> + return ret;
> +}
> +
> +AVInputFormat ff_ac4_demuxer = {
> + .name = "ac4",
> + .long_name = NULL_IF_CONFIG_SMALL("raw AC-4"),
> + .read_probe = ac4_probe,
> + .read_header = ac4_read_header,
> + .read_packet = ac4_read_packet,
> + .flags = AVFMT_GENERIC_INDEX,
> + .extensions = "ac4",
> +};
> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
> index 0209bf0e30..d2afcb2bdd 100644
> --- a/libavformat/allformats.c
> +++ b/libavformat/allformats.c
> @@ -33,6 +33,7 @@ extern AVInputFormat ff_aa_demuxer;
> extern AVInputFormat ff_aac_demuxer;
> extern AVInputFormat ff_ac3_demuxer;
> extern AVOutputFormat ff_ac3_muxer;
> +extern AVInputFormat ff_ac4_demuxer;
> extern AVInputFormat ff_acm_demuxer;
> extern AVInputFormat ff_act_demuxer;
> extern AVInputFormat ff_adf_demuxer;
>
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