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Ffmpeg 4.3 add custom demuxer
2022-07-25 02:55:00 【Spend my whole life reading】
1 compile ffmpeg4.3
1.1 ffmpeg 4.3 download
From abroad git Warehouse downloading ffmeg4.3 The source code is slow , It is recommended to use domestic gitee Image download .
git clone https://gitee.com/mirrors/ffmpeg.git -b release/4.3
1.2 Compile code
./configure --enable-shared --prefix=/home/zhy/code/mypc/ffmpeg4.3/ffmpeg/install_lib
make
make install
1.3 Environment variable configuration
Build after compilation ffmpeg、ffprobe Etc , perform ffmeg See if the compilation is successful ：
./ffmpeg -version
After executing the order, it will report so A mistake we can't find ：
ffmpeg: error while loading shared libraries: libavdevice.so.58: cannot open shared object file: No such file or directory
The reason is that the environment variable is not configured , Can't find so Link path , You need to do the following ：
sudo vim /etc/ld.so.conf
stay conf Add prefix Specified in the lib install route , Enter after adding ：
include /etc/ld.so.conf.d/*.conf
/home/zhy/code/mypc/ffmpeg4.3/ffmpeg/install_lib/lib
Finally, update the configuration ：
sudo ldconfig
Re execution ./ffmpeg -version The order will be normal .
[email protected]:~/code/mypc/ffmpeg4.3/ffmpeg$ ./ffmpeg -version
ffmpeg version n4.3.2-168-g3aba8b176f Copyright (c) 2000-2021 the FFmpeg developers
built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
configuration: --enable-shared --prefix=/home/zhy/code/mypc/ffmpeg4.3/ffmpeg/install_lib
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
[email protected]:~/code/mypc/ffmpeg4.3/ffmpeg$
2 Add custom demuxer
ffmpeg In a dumuxer Need to include read_header、read_packet And so on , Such as mpegts demuxer As shown below ：
AVInputFormat ff_mpegtsraw_demuxer = {
.name = "mpegtsraw",
.long_name = NULL_IF_CONFIG_SMALL("raw MPEG-TS (MPEG-2 Transport Stream)"),
.priv_data_size = sizeof(MpegTSContext),
.read_header = mpegts_read_header,
.read_packet = mpegts_raw_read_packet,
.read_close = mpegts_read_close,
.read_timestamp = mpegts_get_dts,
.flags = AVFMT_SHOW_IDS | AVFMT_TS_DISCONT,
.priv_class = &mpegtsraw_class,
};
Generally speaking audio and video Of demuxer More complicated , So choose to add one image Of demuxer,image The format of... Is selected webp,webp Format spec See reference article .
2.1 add to demuxer Definition
stay libavformat\rawdec.h Add ff_webp_demuxer Definition ：
#define FF_DEF_RAWIMAGE_DEMUXER(shortname, longname, probe, ext, id, flag)\ FF_RAW_DEMUXER_CLASS(shortname)\ AVInputFormat ff_ ## shortname ## _demuxer = {\ .name = #shortname,\ .long_name = NULL_IF_CONFIG_SMALL(longname),\ .read_probe = probe,\ .read_header = ff_raw_image_read_header,\ .read_packet = ff_raw_image_read_packet,\ .extensions = ext,\ .flags = flag,\ .raw_codec_id = id,\ .priv_data_size = sizeof(FFRawVideoDemuxerContext),\ .priv_class = &shortname ## _demuxer_class,\ };
2.2 add to demuxer Definition
stay libavformat\rawdec.c Add implementation related functions in ff_raw_image_read_header、ff_raw_image_read_packet Function and webp Of probe function .
probe Function is mainly used to speculate container Of fmt,webp The format of pictures is mainly through "RIFF" and ”WEBP“ Two conjectures ,probe The function is shown below ：
static int webp_probe(const AVProbeData *p)
{
uint8_t *b = p->buf;
printf("[debug] webp_probe\n");
if (AV_RB32(b) == MKBETAG('R', 'I', 'F', 'F')
&& AV_RB32(b + 8) == MKBETAG('W', 'E', 'B', 'P'))
{
printf("[debug] is webp image \n");
return AVPROBE_SCORE_MAX - 1;
}
return 0;
}
ff_raw_image_read_packet Functions do not need special treatment , Every read must size Of buffer That's all right. .
int ff_raw_image_read_packet(AVFormatContext *s, AVPacket *pkt)
{
int ret, size = 1024;
ret = av_get_packet(s->pb, pkt, size);
if (ret < 0) {
return ret;
}
pkt->size = ret;
pkt->stream_index = 0;
pkt->flags = AV_PKT_FLAG_KEY;
return ret;
}
read_header Function usually reads pictures width、height As well as some flag Information ,ff_raw_image_read_header The function is implemented as follows ：
int ff_raw_image_read_header(AVFormatContext *s)
{
AVStream *st;
FFRawVideoDemuxerContext *s1 = s->priv_data;
int ret = 0;
printf("[debug] %s: %d\n", __func__, __LINE__);
st = avformat_new_stream(s, NULL);
if (!st) {
ret = AVERROR(ENOMEM);
goto fail;
}
st->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
st->codecpar->codec_id = s->iformat->raw_codec_id;
st->need_parsing = AVSTREAM_PARSE_FULL_RAW;
if (AV_CODEC_ID_WEBP == st->codecpar->codec_id)
{
webp_read_info(s, st);
}
fail:
return ret;
}
among webp_read_info Mainly based on webp container Extracted some information ,webp container The most commonly used structures are shown below , See the reference article for details webp Official documents ：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WebP file header (12 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ChunkHeader('VP8X') |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Rsv|I|L|E|X|A|R| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Canvas Width Minus One | ...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
... Canvas Height Minus One |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
among , WebP file header as follows ：
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 'R' | 'I' | 'F' | 'F' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| File Size |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 'W' | 'E' | 'B' | 'P' |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
According to the above structure ,webp_read_info The content in is as follows ：
static int webp_read_info (AVFormatContext *s ,AVStream *st)
{
#define VP8X_FLAG_ANIMATION 0x02
#define VP8X_FLAG_XMP_METADATA 0x04
#define VP8X_FLAG_EXIF_METADATA 0x08
#define VP8X_FLAG_ALPHA 0x10
#define VP8X_FLAG_ICC 0x20
int ret = 0;
int len = 0;
int64_t pos = 0;
int64_t cur_pos = 0;
AVIOContext *pb = s->pb;
int flag = 0;
printf("[debug] %s: %d\n", __func__, __LINE__);
if (NULL == pb)
{
printf("[error] %s: %d invalid input \n", __func__, __LINE__);
goto END;
}
pos = avio_tell(pb);
avio_seek(pb, 0, SEEK_SET);
/*read RIFF tag*/
ret = avio_rb32(pb);
if (ret == MKBETAG('R', 'I', 'F', 'F'))
{
printf("[debug] read RIFF tag \n");
}
else
{
goto END;
}
/*read size*/
ret = avio_rb32(pb);
/*read WEBP tag*/
ret = avio_rb32(pb);
if (ret == MKBETAG('W', 'E', 'B', 'P'))
{
printf("[debug] read WEBP tag \n");
}
/*read VP8X tag*/
ret = avio_rb32(pb);
if (ret == MKBETAG('V', 'P', '8', 'X'))
{
printf("[debug] read VP8X tag \n");
}
/*read size*/
ret = avio_rb32(pb);
/*read flag*/
flag = avio_r8(pb);
printf(" ICCP: %d\n Alpha: %d\n EXIF: %d\n XMP: %d\n Animation: %d\n",
(flag & VP8X_FLAG_ICC) != 0,
(flag & VP8X_FLAG_ALPHA) != 0,
(flag & VP8X_FLAG_EXIF_METADATA) != 0,
(flag & VP8X_FLAG_XMP_METADATA) != 0,
(flag & VP8X_FLAG_ANIMATION) != 0);
avio_seek(pb, pos, SEEK_SET);
END:
return ret;
}
Mainly read VP8X Chunk Some of flag, More detailed webp demux You can refer to libwebp Realization .
2.3 Replace ffmpeg Medium webp demuxer
ffmpeg The Central Plains originally had webp Of demuxer , So you need to libavformat\allformats.c Before the note ff_image_webp_pipe_demuxer And add custom ff_webp_demuxer
/* image demuxers */
//extern AVInputFormat ff_image_webp_pipe_demuxer;
extern AVInputFormat ff_image_xpm_pipe_demuxer;
extern AVInputFormat ff_image_xwd_pipe_demuxer;
extern AVInputFormat ff_webp_demuxer;/*new add*/
Comment out ff_image_webp_pipe_demuxer Compilation only requires ff_image_webp_pipe_demuxer Just kill the place you call , Finally, it needs to be in config.h Close your own webp demuxer, Set to 0.
#define CONFIG_IMAGE_WEBP_PIPE_DEMUXER 0
2.4 Running results
Recompile and install, test ffprobe:
./ffprobe samples/webp/animation/animated-webp-supported.webp
Running results ：
[email protected]:~/code/mypc/ffmpeg4.3/ffmpeg$ ./ffprobe samples/webp/animation/animated-webp-supported.webp
ffprobe version n4.3.2-168-g3aba8b176f Copyright (c) 2007-2021 the FFmpeg developers
built with gcc 7 (Ubuntu 7.5.0-3ubuntu1~18.04)
configuration: --enable-shared --prefix=/home/zhy/code/mypc/ffmpeg4.3/ffmpeg/install_lib
libavutil 56. 51.100 / 56. 51.100
libavcodec 58. 91.100 / 58. 91.100
libavformat 58. 45.100 / 58. 45.100
libavdevice 58. 10.100 / 58. 10.100
libavfilter 7. 85.100 / 7. 85.100
libswscale 5. 7.100 / 5. 7.100
libswresample 3. 7.100 / 3. 7.100
[debug] webp_probe
[debug] is webp image
[debug] ff_raw_image_read_header: 338
[debug] webp_read_info: 251
[debug] read RIFF tag
[debug] read WEBP tag
[debug] read VP8X tag
ICCP: 0
Alpha: 1
EXIF: 0
XMP: 0
Animation: 1
[webp @ 0x5618e1c420c0] skipping unsupported chunk: ANIM
[webp @ 0x5618e1c420c0] skipping unsupported chunk: ANMF
Last message repeated 11 times
[webp @ 0x5618e1c420c0] image data not found
[webp @ 0x5618e1c40d80] decoding for stream 0 failed
[webp @ 0x5618e1c40d80] Could not find codec parameters for stream 0 (Video: webp, none): unspecified size
Consider increasing the value for the 'analyzeduration' and 'probesize' options
Input #0, webp, from 'samples/webp/animation/animated-webp-supported.webp':
Duration: N/A, bitrate: N/A
Stream #0:0: Video: webp, none, 90k tbr, 90k tbn, 90k tbc
[email protected]:~/code/mypc/ffmpeg4.3/ffmpeg$
libwebp in webpinfo Read the results ：
[email protected]:~/code/mypc/mutil_media/libwebp/examples$ ./webpinfo samples/webp/animation/animated-webp-supported.webp
File: samples/webp/animation/animated-webp-supported.webp
RIFF HEADER:
File size: 37342
Chunk VP8X at offset 12, length 18
[leif] webp_info->feature_flags_ = 18
ICCP: 0
Alpha: 1
EXIF: 0
XMP: 0
Animation: 1
Canvas size 400 x 400
It can be seen that , Read the flag And use libwebp Consistent reading , Prove the added customization webp Of demuxer function OK.
Reference article
1 https://developers.google.com/speed/webp/docs/riff_container
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