On 3/5/20, James Almer <jamr...@gmail.com> wrote: > On 3/4/2020 7:51 PM, Paul B Mahol wrote: >> On 3/4/20, James Almer <jamr...@gmail.com> wrote: >>> 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. >> >> That is over complication for simple parsing like here. >> Every raw packet have exact frame size set in bitstream. > > So does AC3, judging by how its parser assembles frames. > > An AVParser will let you resync after a bad seek, read frames in non > seekable input like a pipe, read frames within badly muxed files, > simplify the demuxer, etc, and is a matter of just looking for that > 16bit sync code and assembling a frame. Essentially just re-implementing > what you already did in ac4_probe().
Disagree, it is over complication for zero gain. > >> >>> >>>> + 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; >>>> >>> >>> _______________________________________________ >>> ffmpeg-devel mailing list >>> ffmpeg-devel@ffmpeg.org >>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >>> >>> To unsubscribe, visit link above, or email >>> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". >> _______________________________________________ >> ffmpeg-devel mailing list >> ffmpeg-devel@ffmpeg.org >> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel >> >> To unsubscribe, visit link above, or email >> ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". >> > > _______________________________________________ > ffmpeg-devel mailing list > ffmpeg-devel@ffmpeg.org > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel > > To unsubscribe, visit link above, or email > ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe". _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".