[FFmpeg-devel] [PATCH 4/5] avformat: add moflex demuxer
Andreas Rheinhardt
andreas.rheinhardt at gmail.com
Thu Sep 3 14:26:24 EEST 2020
Paul B Mahol:
> On 9/3/20, Andreas Rheinhardt <andreas.rheinhardt at gmail.com> wrote:
>> Paul B Mahol:
>>> Signed-off-by: Paul B Mahol <onemda at gmail.com>
>>> ---
>>> libavformat/Makefile | 1 +
>>> libavformat/allformats.c | 1 +
>>> libavformat/moflex.c | 360 +++++++++++++++++++++++++++++++++++++++
>>> 3 files changed, 362 insertions(+)
>>> create mode 100644 libavformat/moflex.c
>>>
>>> diff --git a/libavformat/Makefile b/libavformat/Makefile
>>> index cbb33fe37c..1e0ac317e5 100644
>>> --- a/libavformat/Makefile
>>> +++ b/libavformat/Makefile
>>> @@ -319,6 +319,7 @@ OBJS-$(CONFIG_MLV_DEMUXER) += mlvdec.o
>>> riffdec.o
>>> OBJS-$(CONFIG_MM_DEMUXER) += mm.o
>>> OBJS-$(CONFIG_MMF_DEMUXER) += mmf.o
>>> OBJS-$(CONFIG_MMF_MUXER) += mmf.o rawenc.o
>>> +OBJS-$(CONFIG_MOFLEX_DEMUXER) += moflex.o
>>> OBJS-$(CONFIG_MOV_DEMUXER) += mov.o mov_chan.o mov_esds.o
>>> replaygain.o
>>> OBJS-$(CONFIG_MOV_MUXER) += movenc.o av1.o avc.o hevc.o
>>> vpcc.o \
>>> movenchint.o mov_chan.o rtp.o
>>> \
>>> diff --git a/libavformat/allformats.c b/libavformat/allformats.c
>>> index 0aa9dd7198..28331facb9 100644
>>> --- a/libavformat/allformats.c
>>> +++ b/libavformat/allformats.c
>>> @@ -249,6 +249,7 @@ extern AVInputFormat ff_mlv_demuxer;
>>> extern AVInputFormat ff_mm_demuxer;
>>> extern AVInputFormat ff_mmf_demuxer;
>>> extern AVOutputFormat ff_mmf_muxer;
>>> +extern AVInputFormat ff_moflex_demuxer;
>>> extern AVInputFormat ff_mov_demuxer;
>>> extern AVOutputFormat ff_mov_muxer;
>>> extern AVOutputFormat ff_mp2_muxer;
>>> diff --git a/libavformat/moflex.c b/libavformat/moflex.c
>>> new file mode 100644
>>> index 0000000000..989623396f
>>> --- /dev/null
>>> +++ b/libavformat/moflex.c
>>> @@ -0,0 +1,360 @@
>>> +/*
>>> + * MOFLEX demuxer
>>> + * Copyright (c) 2020 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 "libavcodec/bytestream.h"
>>> +
>>> +#include "avformat.h"
>>> +#include "internal.h"
>>> +
>>> +typedef struct BitReader {
>>> + unsigned last;
>>> + unsigned pos;
>>> +} BitReader;
>>> +
>>> +typedef struct MOFLEXDemuxContext {
>>> + unsigned size;
>>> + int64_t pos;
>>> + int64_t ts;
>>> + int flags;
>>> + int in_block;
>>> +
>>> + BitReader br;
>>> +} MOFLEXDemuxContext;
>>> +
>>> +static int pop(BitReader *br, AVIOContext *pb)
>>> +{
>>> + if (avio_feof(pb))
>>> + return AVERROR_EOF;
>>> +
>>> + if ((br->pos & 7) == 0)
>>> + br->last = (unsigned)avio_r8(pb) << 24U;
>>> + else
>>> + br->last <<= 1;
>>> +
>>> + br->pos++;
>>> + return !!(br->last & 0x80000000);
>>> +}
>>> +
>>> +static int pop_int(BitReader *br, AVIOContext *pb, int n)
>>> +{
>>> + int value = 0;
>>> +
>>> + for (int i = 0; i < n; i++) {
>>> + int ret = pop(br, pb);
>>> +
>>> + if (ret < 0)
>>> + return ret;
>>> + value = 2 * value + ret;
>>> + }
>>> +
>>> + return value;
>>> +}
>>> +
>>> +static int pop_length(BitReader *br, AVIOContext *pb)
>>> +{
>>> + int ret, n = 1;
>>> +
>>> + while ((ret = pop(br, pb)) == 0)
>>> + n++;
>>> +
>>> + if (ret < 0)
>>> + return ret;
>>> + return n;
>>> +}
>>> +
>>> +static int read_var_byte(AVFormatContext *s, unsigned *out)
>>> +{
>>> + AVIOContext *pb = s->pb;
>>> + unsigned value = 0, data;
>>> +
>>> + data = avio_r8(pb);
>>> + if (!(data & 0x80)) {
>>> + *out = data;
>>> + return 0;
>>> + }
>>> +
>>> + value = (data & 0x7F) << 7;
>>> + data = avio_r8(pb);
>>> + if (!(data & 0x80)) {
>>> + value |= data;
>>> + *out = value;
>>> + return 0;
>>> + }
>>> +
>>> + value = ((data & 0x7F) | value) << 7;
>>> + data = avio_r8(pb);
>>> + if (!(data & 0x80)) {
>>> + value |= data;
>>> + *out = value;
>>> + return 0;
>>> + }
>>> +
>>> + value = (((data & 0x7F) | value) << 7) | avio_r8(pb);
>>> + *out = value;
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int moflex_probe(const AVProbeData *p)
>>> +{
>>> + GetByteContext gb;
>>> + int score = 0;
>>> +
>>> + bytestream2_init(&gb, p->buf, p->buf_size);
>>> +
>>> + if (bytestream2_get_be16(&gb) != 0x4C32)
>>> + return 0;
>>> + score += 10;
>>> +
>>> + bytestream2_skip(&gb, 10);
>>> + if (bytestream2_get_be16(&gb) == 0)
>>> + return 0;
>>> + score += 5;
>>> +
>>> + while (bytestream2_get_bytes_left(&gb) > 0) {
>>> + int type = bytestream2_get_byte(&gb);
>>> + int size = bytestream2_get_byte(&gb);
>>> +
>>> + if (type == 0) {
>>> + score += 5 * (size == 0);
>>> + break;
>>> + }
>>> + if ((type == 1 && size == 12) ||
>>> + (type == 2 && size == 6) ||
>>> + (type == 3 && size == 13) ||
>>> + (type == 4 && size == 2))
>>> + score += 20;
>>> + bytestream2_skip(&gb, size);
>>> + }
>>> +
>>> + return FFMIN(AVPROBE_SCORE_MAX, score);
>>> +}
>>> +
>>> +static int moflex_read_sync(AVFormatContext *s)
>>> +{
>>> + MOFLEXDemuxContext *m = s->priv_data;
>>> + AVIOContext *pb = s->pb;
>>> +
>>> + if (avio_rb16(pb) != 0x4C32) {
>>> + if (avio_feof(pb))
>>> + return AVERROR_EOF;
>>> + avio_seek(pb, -2, SEEK_CUR);
>>> + return 1;
>>> + }
>>> +
>>> + avio_skip(pb, 2);
>>> + m->ts = avio_rb64(pb);
>>> + m->size = avio_rb16(pb) + 1;
>>> +
>>> + while (!avio_feof(pb)) {
>>> + unsigned type, ssize, codec_id = 0;
>>> + unsigned codec_type, width = 0, height = 0, sample_rate = 0,
>>> channels = 0;
>>> + int stream_index = -1;
>>> + int format;
>>> + AVRational fps;
>>> +
>>> + read_var_byte(s, &type);
>>> + read_var_byte(s, &ssize);
>>> +
>>> + switch (type) {
>>> + case 0:
>>> + if (ssize > 0)
>>> + avio_skip(pb, ssize);
>>> + return 0;
>>> + case 2:
>>> + codec_type = AVMEDIA_TYPE_AUDIO;
>>> + stream_index = avio_r8(pb);
>>> + codec_id = avio_r8(pb);
>>> + switch (codec_id) {
>>> + case 0: codec_id = AV_CODEC_ID_FASTAUDIO; break;
>>> + case 1: codec_id = AV_CODEC_ID_ADPCM_IMA_MOFLEX; break;
>>> + case 2: codec_id = AV_CODEC_ID_PCM_S16LE; break;
>>> + default:
>>> + av_log(s, AV_LOG_ERROR, "Unsupported audio codec: %d\n",
>>> codec_id);
>>> + return AVERROR_PATCHWELCOME;
>>> + }
>>> + sample_rate = avio_rb24(pb) + 1;
>>> + channels = avio_r8(pb) + 1;
>>> + break;
>>> + case 1:
>>> + case 3:
>>> + codec_type = AVMEDIA_TYPE_VIDEO;
>>> + stream_index = avio_r8(pb);
>>> + codec_id = avio_r8(pb);
>>> + switch (codec_id) {
>>> + case 0: codec_id = AV_CODEC_ID_MOBICLIP; break;
>>> + default:
>>> + av_log(s, AV_LOG_ERROR, "Unsupported video codec: %d\n",
>>> codec_id);
>>> + return AVERROR_PATCHWELCOME;
>>> + }
>>> + fps.num = avio_rb16(pb);
>>> + fps.den = avio_rb16(pb);
>>> + width = avio_rb16(pb);
>>> + height = avio_rb16(pb);
>>> + format = AV_PIX_FMT_YUV420P;
>>> + avio_skip(pb, type == 3 ? 3 : 2);
>>> + break;
>>> + case 4:
>>> + codec_type = AVMEDIA_TYPE_DATA;
>>> + stream_index = avio_r8(pb);
>>> + avio_skip(pb, 1);
>>> + break;
>>> + }
>>> +
>>> + if (stream_index == s->nb_streams) {
>>> + AVStream *st = avformat_new_stream(s, NULL);
>>> +
>>> + if (!st)
>>> + return AVERROR(ENOMEM);
>>> +
>>> + st->codecpar->codec_type = codec_type;
>>> + st->codecpar->codec_id = codec_id;
>>> + st->codecpar->width = width;
>>> + st->codecpar->height = height;
>>> + st->codecpar->sample_rate= sample_rate;
>>> + st->codecpar->channels = channels;
>>> + st->codecpar->format = format;
>>> + st->priv_data = av_packet_alloc();
>>> + if (!st->priv_data)
>>> + return AVERROR(ENOMEM);
>>
>> If this allocation fails when reading a packet, you end up with a stream
>> without priv_data. If the caller decides to call av_read_frame() again,
>> you can get a segfault, because the code for reading a packet presumes
>> every stream to have an AVPacket as priv_data.
>
> Why should caller call it again after receiving the fatal error?
> That is never checked/covered anyway by anything.
>
Where is it documented that AVERROR(ENOMEM) is a fatal error? And upon
receiving said error, the caller could free some memory and try again.
> I do not need to comply with out of head new standards.
> And also checking thing in function itself is much cleaner, and more robust
> for all another demuxers and callers, instead of doing it before calling this
> function and takes less lines of code.
>
Not really: For the vast majority of other callers, it is clear that the
packet exists, so adding a check only slows them down. Furthermore, from
the point of av_append_packet(), a NULL AVPacket is AVERROR(EINVAL), but
that would not be an appropriate return value for your caller (who has
not set any argument (hence no wrong argument) given that your demuxer
doesn't have any options), so you would have to filter this and
overwrite the error with something else (probably AVERROR(ENOMEM) again)
and this would negate your "less lines of code" argument. The reason for
you not being allowed to return the error code as is is of course that
in this scenario the error originates in the demuxer itself (for using
NULL as AVPacket) and not somewhere else.
>>
>>> +
>>> + if (sample_rate)
>>> + avpriv_set_pts_info(st, 63, 1, sample_rate);
>>> + else
>>> + avpriv_set_pts_info(st, 63, fps.den, fps.num);
>>> + }
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int moflex_read_header(AVFormatContext *s)
>>> +{
>>> + int ret;
>>> +
>>> + ret = moflex_read_sync(s);
>>> + if (ret < 0)
>>> + return ret;
>>> +
>>> + s->ctx_flags |= AVFMTCTX_NOHEADER;
>>> + avio_seek(s->pb, 0, SEEK_SET);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +static int moflex_read_packet(AVFormatContext *s, AVPacket *pkt)
>>> +{
>>> + MOFLEXDemuxContext *m = s->priv_data;
>>> + AVIOContext *pb = s->pb;
>>> + BitReader *br = &m->br;
>>> + int ret;
>>> +
>>> + while (!avio_feof(pb)) {
>>> + if (!m->in_block) {
>>> + m->pos = avio_tell(pb);
>>> +
>>> + ret = moflex_read_sync(s);
>>> + if (ret < 0)
>>> + return ret;
>>> +
>>> + m->flags = avio_r8(pb);
>>> + if (m->flags & 2)
>>> + avio_skip(pb, 2);
>>> + }
>>> +
>>> + while ((avio_tell(pb) < m->pos + m->size) && !avio_feof(pb) &&
>>> avio_r8(pb)) {
>>> + int stream_index, bits, pkt_size, endframe;
>>> + AVPacket *packet;
>>> +
>>> + m->in_block = 1;
>>> +
>>> + avio_seek(pb, -1, SEEK_CUR);
>>> + br->pos = br->last = 0;
>>> +
>>> + bits = pop_length(br, pb);
>>> + if (bits < 0)
>>> + return bits;
>>> + stream_index = pop_int(br, pb, bits);
>>> + if (stream_index < 0)
>>> + return stream_index;
>>> + if (stream_index >= s->nb_streams)
>>> + return AVERROR_INVALIDDATA;
>>> +
>>> + endframe = pop(br, pb);
>>> + if (endframe < 0)
>>> + return endframe;
>>> + if (endframe) {
>>> + bits = pop_length(br, pb);
>>> + if (bits < 0)
>>> + return bits;
>>> + pop_int(br, pb, bits);
>>> + pop(br, pb);
>>> + bits = pop_length(br, pb);
>>> + if (bits < 0)
>>> + return bits;
>>> + pop_int(br, pb, bits * 2 + 26);
>>> + }
>>> +
>>> + pkt_size = pop_int(br, pb, 13) + 1;
>>> + packet = s->streams[stream_index]->priv_data;
>>> +
>>> + ret = av_append_packet(pb, packet, pkt_size);
>>> + if (endframe) {
>>> + av_packet_move_ref(pkt, packet);
>>> + pkt->pos = m->pos;
>>> + pkt->stream_index = stream_index;
>>> + pkt->flags |= AV_PKT_FLAG_KEY;
>>> + return ret;
>>> + }
>>> + }
>>> +
>>> + m->in_block = 0;
>>> +
>>> + if (m->flags % 2 == 0)
>>> + avio_seek(pb, m->pos + m->size, SEEK_SET);
>>> + }
>>> +
>>> + return AVERROR_EOF;
>>> +}
>>> +
>>> +static int moflex_read_close(AVFormatContext *s)
>>> +{
>>> + for (int i = 0; i < s->nb_streams; i++) {
>>> + AVPacket *packet = s->streams[i]->priv_data;
>>> +
>>> + av_packet_free(&packet);
>>> + s->streams[i]->priv_data = 0;
>>> + }
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +AVInputFormat ff_moflex_demuxer = {
>>> + .name = "moflex",
>>> + .long_name = NULL_IF_CONFIG_SMALL("MobiClip MOFLEX"),
>>> + .priv_data_size = sizeof(MOFLEXDemuxContext),
>>> + .read_probe = moflex_probe,
>>> + .read_header = moflex_read_header,
>>> + .read_packet = moflex_read_packet,
>>> + .read_close = moflex_read_close,
>>> + .extensions = "moflex",
>>> + .flags = AVFMT_GENERIC_INDEX,
>>> +};
>>>
>>
>> _______________________________________________
>> ffmpeg-devel mailing list
>> ffmpeg-devel at ffmpeg.org
>> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>>
>> To unsubscribe, visit link above, or email
>> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
>
More information about the ffmpeg-devel
mailing list