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Sur d’autres sites (7199)
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Puzzled with file descriptor in Bash (ffmpeg video capture)
3 mai 2020, par ChrisAgaI am trying to use file descriptors in Bash and found a problem I cannot solve.
I have to read a video stream coming from the standard output of a command executed in a
coproc. This piece of code works as expected :


ffmpeg \
 -i <(exec cat <&${COPROC[0]}) \
 -c:v $ENCODE_VIDEO_FORMAT_LOSSLESS $ENCODE_VIDEO_OPTIONS_LOSSLESS \
 -c:a copy \
 -progress /dev/fd/1 \
 "${capfile}"



But the
catprocess is not really useful sinceffmpeg -i pipe:<file descriptor="descriptor"></file>seems to do the same. So I tried the following code which fails withpipe:63: Bad file descriptor
error.


ffmpeg \
 -i pipe:"${COPROC[0]}" \
 -c:v $ENCODE_VIDEO_FORMAT_LOSSLESS $ENCODE_VIDEO_OPTIONS_LOSSLESS \
 -c:a copy \
 -progress /dev/fd/1 \
 "${capfile}"



The actual script is something a bit complicated but here is a minimal testing code for this issue :



#!/bin/bash
#

ENCODE_VIDEO_FORMAT_LOSSLESS=ffv1
ENCODE_VIDEO_OPTIONS_LOSSLESS="-level 3 -threads 7 -coder 1 -context 1 -g 1 -slices 30 -slicecrc 1"

capfile=capure.mkv

coproc ffmpeg -i file:'Camomille.mkv' -c:v copy -c:a copy -f matroska pipe:1

capture_fd=${COPROC[0]}
echo "hk_capture_pid=${COPROC_PID}"

ffmpeg \
 -i pipe:${COPROC[0]} \
 -c:v $ENCODE_VIDEO_FORMAT_LOSSLESS $ENCODE_VIDEO_OPTIONS_LOSSLESS \
 -c:a copy \
 -progress /dev/fd/1 \
 "${capfile}"



This is the output of the second
ffmpegcommand :


ffmpeg version 4.1.4-1build2 Copyright (c) 2000-2019 the FFmpeg developers
 built with gcc 9 (Ubuntu 9.2.1-4ubuntu1)
 configuration: --prefix=/usr --extra-version=1build2 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
 libavutil 56. 22.100 / 56. 22.100
 libavcodec 58. 35.100 / 58. 35.100
 libavformat 58. 20.100 / 58. 20.100
 libavdevice 58. 5.100 / 58. 5.100
 libavfilter 7. 40.101 / 7. 40.101
 libavresample 4. 0. 0 / 4. 0. 0
 libswscale 5. 3.100 / 5. 3.100
 libswresample 3. 3.100 / 3. 3.100
 libpostproc 55. 3.100 / 55. 3.100
pipe:63: Bad file descriptor
av_interleaved_write_frame(): Broken pipe 
Error writing trailer of pipe:1: Broken pipe 
frame= 4 fps=0.0 q=-1.0 Lsize= 48kB time=00:00:00.03 bitrate=10051.1kbits/s speed=3.44x 
video:86kB audio:1kB subtitle:0kB other streams:0kB global headers:2kB muxing overhead: unknown
Conversion failed!



This one fails and if you replace
-i pipe:${COPROC[0]}by-i <(exec cat <&${COPROC[0]})a capture.mkv file is created.


I run ubuntu eoan and bash version is :
GNU bash, version 5.0.3(1)-release (x86_64-pc-linux-gnu). I upgraded several times since I started with this issue, so it wouldn't be related too much to bash and ffmpeg versions.


If someone can point me to what I do wrong with bash file descriptors I would be grateful.


-
Streaming H.264 over UDP using FFmpeg, and "dimensions not set" error
3 septembre 2015, par Baris DemirayI’m trying to stream H.264 over UDP with no luck so far. Here is a minimal code that you can reproduce the problem.
To compile,
g++ -o test -lavcodec -lavformat -lavutil test.cppExtra information, I start
ffplayas follows. Currently it’s of no use.ffplay -i udp://127.0.0.1:8554/live.sdpOutput of my code (see
avio_open()call),[libx264 @ 0x6a26c0] using mv_range_thread = 24
[libx264 @ 0x6a26c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.1 Cache64
[libx264 @ 0x6a26c0] profile High, level 3.1
Output #0, h264, to 'udp://127.0.0.1:8554/live.sdp':
Stream #0:0, 0, 0/0: Video: h264 (libx264), -1 reference frame, none, q=-1--1
[h264 @ 0x6a2020] dimensions not set
Cannot write header to stream: SuccessAnd the code,
extern "C" {
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
#include <libavutil></libavutil>avutil.h>
}
#include <iostream>
using namespace std;
int main() {
AVCodecContext* m_codecContext;
AVCodec* m_codec;
AVFormatContext* m_formatContext;
AVStream* m_stream;
unsigned m_outWidth = 768;
unsigned m_outHeight = 608;
av_register_all();
avcodec_register_all();
avformat_network_init();
int errorStatus = 0;
char errorLog[128] = { 0 };
av_log_set_level(AV_LOG_TRACE);
string m_output("udp://127.0.0.1:8554/live.sdp");
if (avformat_alloc_output_context2(&m_formatContext, NULL, "h264", m_output.c_str()) < 0) {
cerr << "Cannot allocate output context: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
AVOutputFormat *m_outputFormat = m_formatContext->oformat;
m_codec = avcodec_find_encoder(AV_CODEC_ID_H264);
if (!m_codec) {
cerr << "Cannot find an encoder: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
m_codecContext = avcodec_alloc_context3(m_codec);
if (!m_codecContext) {
cerr << "Cannot allocate a codec context: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
m_codecContext->pix_fmt = AV_PIX_FMT_YUV420P;
m_codecContext->width = m_outWidth;
m_codecContext->height = m_outHeight;
if (avcodec_open2(m_codecContext, m_codec, NULL) < 0) {
cerr << "Cannot open codec: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
m_stream = avformat_new_stream(m_formatContext, m_codec);
if (!m_stream) {
cerr << "Cannot create a new stream: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
av_dump_format(m_formatContext, 0, m_output.c_str(), 1);
if ((errorStatus = avio_open(&m_formatContext->pb, m_output.c_str(), AVIO_FLAG_WRITE)) < 0) {
cerr << "Cannot open output: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
if (avformat_write_header(m_formatContext, NULL) < 0) {
cerr << "Cannot write header to stream: "
<< av_make_error_string(errorLog, 128, errorStatus) << endl;
return -1;
}
cout << "All done." << endl;
return 0;
}
</iostream>For those who has even more time to spare on my problem, when I change
m_outputtortsp://127.0.0.1:8554/live.sdp, andffplaycommand toffplay -rtsp_flags listen -i rtsp://127.0.0.1:8554/live.sdpI get the error,[libx264 @ 0x1e056c0] using mv_range_thread = 24
[libx264 @ 0x1e056c0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.1 Cache64
[libx264 @ 0x1e056c0] profile High, level 3.1
Output #0, h264, to 'rtsp://127.0.0.1:8554/live.sdp':
Stream #0:0, 0, 0/0: Video: h264 (libx264), -1 reference frame, none, q=-1--1
Cannot open output: Protocol not foundAm I naive to expect that streaming protocol will be changed like this ?
-
How to modify the bit_rate of AVFormatContext ?
27 mars 2023, par Zion LiuHello，I would like to know how to modify the bit_rate of AVFormatContext.


Here is the minimal reproducible example.This is a simple process for pushing rtmp video streams.Now I want to control the bitrate of the video it pushes.


I tried modifying the bitrate like this, but it didn't work.


AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
int64_t bit_rate = 400*1000;
....
ofmt_ctx->bit_rate = bit_rate;


Can be compiled by
g++ -Wall -o -g -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include -I/usr/local/include -L/usr/local/lib simplt_push_streaming.cpp -o test.out -lavformat -lavcodec -lavutil -lgobject-2.0 -lglib-2.0 -lpthread

And my ffmpeg version :
ffmpeg version 4.4.2-0ubuntu0.22.04.1

#include 
extern "C"
{
#include <libavformat></libavformat>avformat.h>
#include <libavutil></libavutil>mathematics.h>
#include <libavutil></libavutil>time.h>
};

int main(int argc, char* argv[])
{
 AVOutputFormat *ofmt = NULL;
 //Input AVFormatContext and Output AVFormatContext
 AVFormatContext *ifmt_ctx = NULL, *ofmt_ctx = NULL;
 AVPacket pkt;
 const char *in_filename, *out_filename;
 int ret, i;
 int videoindex=-1;
 int frame_index=0;
 int64_t start_time=0;
 int64_t bit_rate = 400*1000;
 in_filename = "/home/zion/video/mecha.flv";// Input file URL
 out_filename = "rtmp://localhost:1935/live/test";//Output URL [RTMP]
 av_register_all();
 avformat_network_init();
 avformat_open_input(&ifmt_ctx, in_filename, 0, 0);
 avformat_find_stream_info(ifmt_ctx, 0);
 for(i=0; inb_streams; i++) 
 if(ifmt_ctx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
 videoindex=i;
 break;
 }
 //Output
 avformat_alloc_output_context2(&ofmt_ctx, NULL, "flv", out_filename); //RTMP
 ofmt = ofmt_ctx->oformat;
 for (i = 0; i < ifmt_ctx->nb_streams; i++) {
 //Create output AVStream according to input AVStream
 AVStream *in_stream = ifmt_ctx->streams[i];
 AVStream *out_stream = avformat_new_stream(ofmt_ctx, in_stream->codec->codec);
 //Copy the settings of AVCodecContext
 ret = avcodec_copy_context(out_stream->codec, in_stream->codec);
 out_stream->codec->codec_tag = 0;
 if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
 out_stream->codec->flags |= AV_CODEC_FLAG_GLOBAL_HEADER;
 }
 //Open output URL
 if (!(ofmt->flags & AVFMT_NOFILE)) {
 ret = avio_open(&ofmt_ctx->pb, out_filename, AVIO_FLAG_WRITE);
 }
 //Write file header
 avformat_write_header(ofmt_ctx, NULL);
 start_time=av_gettime();
 while (1) {
 AVStream *in_stream, *out_stream;
 //Get an AVPacket
 ret = av_read_frame(ifmt_ctx, &pkt);
 if (ret < 0)
 break;
 //Important:Delay
 if(pkt.stream_index==videoindex){
 AVRational time_base=ifmt_ctx->streams[videoindex]->time_base;
 AVRational time_base_q={1,AV_TIME_BASE};
 int64_t pts_time = av_rescale_q(pkt.dts, time_base, time_base_q);
 int64_t now_time = av_gettime() - start_time;
 if (pts_time > now_time)
 av_usleep(pts_time - now_time);
 }
 in_stream = ifmt_ctx->streams[pkt.stream_index];
 out_stream = ofmt_ctx->streams[pkt.stream_index];
 if(pkt.stream_index==videoindex){
 printf("Send %8d video frames to output URL\n",frame_index);
 frame_index++;
 }
/*I tried modifying the bitrate here and I'm not sure if this is the correct usage.*/
 ofmt_ctx->bit_rate = bit_rate;
 av_interleaved_write_frame(ofmt_ctx, &pkt);
 av_free_packet(&pkt);
 }
 //Write file trailer
 av_write_trailer(ofmt_ctx);
end:
 avformat_close_input(&ifmt_ctx);
 /* close output */
 if (ofmt_ctx && !(ofmt->flags & AVFMT_NOFILE))
 avio_close(ofmt_ctx->pb);
 avformat_free_context(ofmt_ctx);
 return 0;
}


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