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Carte de Schillerkiez
13 mai 2011, par
Mis à jour : Septembre 2011
Langue : English
Type : Texte
Autres articles (34)
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Sur d’autres sites (7817)
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FFmpeg problems with playing a stream
13 avril 2021, par NikoI want to play a stream over network. While my server works I can't get it working receiving audio on client. It's router with openwrt installed and usb soundcard.


When i run

ffmpeg -i "udp://@:5555" -f alsa hw:0i get a following error

[NULL @ 0x76b2b390] Requested output format 'alsa' is not a suitable output format
hw:0: Invalid argument


What's wrong with my command ?
On router there is limited space. I hardly handled to install ffmpeg.


There is complete log :


root@LEDE:/proc/asound# ffmpeg -i "udp://@:5555" -f alsa hw:0
ffmpeg version 3.2.2 Copyright (c) 2000-2016 the FFmpeg developers
 built with gcc 5.4.0 (LEDE GCC 5.4.0 r3101-bce140e)
 configuration: --enable-cross-compile --cross-prefix=mips-openwrt-linux-musl- --arch=mips --target-os=linux --prefix=/usr --pkg-config=pkg-config --enable-shared --enable-static --enable-small --enable-pthreads --enable-zlib --disable-doc --disable-debug --enable-gpl --enable-version3 --disable-dxva2 --disable-lzma --disable-vaapi --disable-vda --disable-vdpau --disable-outdevs --disable-altivec --disable-vsx --disable-power8 --disable-amd3dnow --disable-amd3dnowext --disable-mmx --disable-mmxext --disable-sse --disable-sse2 --disable-sse3 --disable-ssse3 --disable-sse4 --disable-sse42 --disable-avx --disable-xop --disable-fma3 --disable-fma4 --disable-avx2 --disable-aesni --disable-armv5te --disable-armv6 --disable-armv6t2 --disable-inline-asm --disable-mipsdsp --disable-mipsdspr2 --disable-mipsfpu --disable-msa --disable-mmi --disable-fast-unaligned --disable-runtime-cpudetect --disable-yasm --enable-libopus --enable-decoder=libopus --enable-libx264 --enable-libmp3lame
 libavutil 55. 34.100 / 55. 34.100
 libavcodec 57. 64.101 / 57. 64.101
 libavformat 57. 56.100 / 57. 56.100
 libavdevice 57. 1.100 / 57. 1.100
 libavfilter 6. 65.100 / 6. 65.100
 libswscale 4. 2.100 / 4. 2.100
 libswresample 2. 3.100 / 2. 3.100
 libpostproc 54. 1.100 / 54. 1.100
Input #0, mpegts, from 'udp://@:5555':
 Duration: N/A, start: 1.400000, bitrate: 384 kb/s
 Program 1 
 Metadata:
 service_name : Service01
 service_provider: FFmpeg
 Stream #0:0[0x100]: Audio: mp2 ([3][0][0][0] / 0x0003), 44100 Hz, stereo, s16p, 384 kb/s
[NULL @ 0x76b2b390] Requested output format 'alsa' is not a suitable output format
hw:0: Invalid argument


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Why does the official LibAV 12 video example not work properly ?
11 avril 2021, par TheNeuronalCoderI would say the title is quite self-explanatory, but I nearly completely copied the example given by LibAV right here and yet the output video it produced was not playable. Why is it not playable ? Am I using the wrong file extension ? I do not understand what I could have possibly done wrong here and there's little to no documentation I could find for how to encode mp4 video in C++.


#include 
#include 
#include 
#include "libavcodec/avcodec.h"
#include "libavutil/frame.h"
#include "libavutil/imgutils.h"

static void encode(AVCodecContext *enc_ctx, AVFrame *frame, AVPacket *pkt, FILE *outfile) {
 int ret;
 ret = avcodec_send_frame(enc_ctx, frame);
 if (ret < 0) {
 fprintf(stderr, "error sending a frame for encoding\n");
 exit(1);
 }
 while (ret >= 0) {
 ret = avcodec_receive_packet(enc_ctx, pkt);
 if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
 return;
 else if (ret < 0) {
 fprintf(stderr, "error during encoding\n");
 exit(1);
 }
 printf("encoded frame %3"PRId64" (size=%5d)\n", pkt->pts, pkt->size);
 fwrite(pkt->data, 1, pkt->size, outfile);
 av_packet_unref(pkt);
 }
}

int main() {
 const char *filename = "animation.mp4";
 const AVCodec *codec;
 AVCodecContext *c = NULL;
 int i, ret, x, y;
 FILE *f;
 AVFrame *picture;
 AVPacket *pkt;
 uint8_t endcode[] = { 0, 0, 1, 0xb7 };
 if (argc <= 1) {
 fprintf(stderr, "Usage: %s <output file="file">\n", argv[0]);
 exit(0);
 }
 avcodec_register_all();
 codec = avcodec_find_encoder(AV_CODEC_ID_MPEG1VIDEO);
 if (!codec) {
 fprintf(stderr, "codec not found\n");
 exit(1);
 }
 c = avcodec_alloc_context3(codec);
 picture = av_frame_alloc();
 pkt = av_packet_alloc();
 if (!pkt)
 exit(1);
 c->bit_rate = 400000;
 c->width = 352;
 c->height = 288;
 c->time_base = (AVRational){1, 25};
 c->framerate = (AVRational){25, 1};
 c->gop_size = 10;
 c->max_b_frames=1;
 c->pix_fmt = AV_PIX_FMT_YUV420P;
 if (avcodec_open2(c, codec, NULL) < 0) {
 fprintf(stderr, "could not open codec\n");
 exit(1);
 }
 f = fopen(filename, "wb");
 if (!f) {
 fprintf(stderr, "could not open %s\n", filename);
 exit(1);
 }
 picture->format = c->pix_fmt;
 picture->width = c->width;
 picture->height = c->height;
 ret = av_frame_get_buffer(picture, 32);
 if (ret < 0) {
 fprintf(stderr, "could not alloc the frame data\n");
 exit(1);
 }

 for(i=0;i<25;i++) {
 fflush(stdout);
 ret = av_frame_make_writable(picture);
 if (ret < 0)
 exit(1);

 for(y=0;yheight;y++) {
 for(x=0;xwidth;x++) {
 picture->data[0][y * picture->linesize[0] + x] = x + y + i * 3;
 }
 }

 for(y=0;yheight/2;y++) {
 for(x=0;xwidth/2;x++) {
 picture->data[1][y * picture->linesize[1] + x] = 128 + y + i * 2;
 picture->data[2][y * picture->linesize[2] + x] = 64 + x + i * 5;
 }
 }

 picture->pts = i;
 encode(c, picture, pkt, f);
 }

 encode(c, NULL, pkt, f);

 fwrite(endcode, 1, sizeof(endcode), f);
 fclose(f);
 avcodec_free_context(&c);
 av_frame_free(&picture);
 av_packet_free(&pkt);
 return 0;
}
</output>

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FPS from RTSP stream info does not match actual framerate
17 mai 2021, par KrapowI have a 25FPS RTSP stream coming from an IP-camera. I can successfully display the video stream. But when analyzing the stream with ffmpeg (ffprobe actually), I observe fewer frames per second rate :


$ ffprobe -rtsp_transport tcp -i rtsp://camera_ip:554/stream -select_streams v:0 -show_frames -show_entries frame=coded_picture_number,pkt_pts_time -of csv=p=0
Stream #0:0: Video: h264 (Main), yuvj420p(pc, bt709, progressive), 640x480, 25 fps, 25 tbr, 90k tbn, 50 tbc
0.400000,0
0.080000,1
0.120000,2
0.200000,3
0.240000,4
0.320000,5
0.360000,6
0.440000,7
0.480000,8
0.560000,9
0.600000,10
0.680000,11
0.720000,12
0.800000,13
0.840000,14
0.920000,15
0.960000,16
1.040000,17
1.080000,18
1.160000,19
1.200000,20
1.280000,21
1.320000,22
1.400000,23
1.440000,24
1.520000,25
1.560000,26
1.640000,27
1.680000,28
1.760000,29
1.800000,30
1.880000,31
1.920000,32
2.000000,33


We can clearly see the 80ms gap between some of the frames, resulting in a 16fps stream.


I have observed the same framerate issue with GStreamer (printing information in the rtpjitterbuffer indicates the frame gap is sometimes 80ms and sometimes 40ms). But the weird thing is, I encountered the same issue with an HDMI-RJ45 decoder, and I doubt the same issue comes from 2 different devices.
I didn't get much more informations using -loglevel debug or trace.
Does anybody have an idea about what is going wrong in the stream ?


(I used ffprobe 4.2.3 and the last "2021-05-09-git-8649f5dca6-full_build-www.gyan.dev" with the same results, and GStreamer 1.16.2 with a pipeline like "urisourcebin ! h264depay ! h264parse ! fakesink")


EDIT : The camera skipping of frames was caused by the activation of a third stream in the options. I find it really weird that it skips exactly the same frames every seconds. However, I still haven't found the cause of the downrate on my RTSP encoder.
Anyway, this was actually hardware related and not software related.


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