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• Streaming Webcam Over LAN : HTML5 Video Element Not Loading

  27 novembre 2023, par Franck Freiburger

  I am currently working on a project where I aim to stream my webcam over my LAN and read the stream in an HTML5 video element with minimal setup. My setup involves a server (192.168.0.1 dev/video0 -> ffmpeg) and a client (192.168.0.2 html5 browser). I am using ffmpeg with the codec set to h264.

  


  Here is the ffmpeg command I am using :

  


  ffmpeg -f video4linux2 -i /dev/video0
  -an -c:v libx264 -b:v 1024k -video_size 800x600 -pix_fmt yuv420p -preset ultrafast
  -tune zerolatency -g 16 -keyint_min 16 -f mpegts pipe:1


  


  This command is spawned by a simple Node.js server that shares this stream without any transformation (just pipe ffpmeg stream to each incoming connection).

  


  When I use vlc or ffplay with the following command, it works very well :

  


  ffplay -fflags nobuffer -flags low_delay -probesize 32 -analyzeduration 0 -framedrop http://192.168.0.1:3000/stream


  


  I can even run multiple instances of ffplay and the video is properly played. However, when I try to use the HTML5 element like this :

  


  <video src="http://127.0.0.1:3000/stream" type="video/mp4"></video>&#xA;

  


  The video seems to "load forever" without any error, nothing suspect in chrome://media-internals. I can see in the network tab that the network is reading the stream, but the video does not play (got same result using hljs and videojs).

  


  

  


  I am looking for help to understand :

  


  

  • What is wrong with the <video></video> element in this context ?

  


  • Is there a better approach to achieve this ?

  


  


  Any help or guidance would be greatly appreciated.

  


• FFmpeg chromakey libavfilter using C-API - key/replace green with alpha transparency

  3 juin 2020, par ZeroDefect

  I'm trying to use the FFmpeg chromakey libavfilter (via the C-API using C++17) to key some green pixels in a YUVA422p image and replace them with alpha transparency.

  



  Now, I setup/initialise the graph, connect the filters, and push through a frame ; however, the output frame appears unchanged. I suspect one of my configuration parameters is incorrect, but I'm really unsure. After having read the pertinent documentation, I still don't understand the problem.

  



  I have published a (minimal) code sample in github - https://github.com/zerodefect/chromakey_test. I have tried to keep the code sample as brief as possible but it is still a bit lengthy.

  



  The code sample includes a sample image (green_screen.png) for the purposes of testing.

  



  To run the application, the following parameters are required :

  



  


  ./cb_chroma_key_test ./green_screen.png [OUTPUT_PATH]

  


  



  The application dumps out a PLANAR image at YUV422p which I then load in via rawpixels.net - a brilliant little online utility to view raw image data (packed or planar).

  



  My avfilter graph consists of :

  



  


  buffersrc -> format -> chromakey -> buffersink

  


  



  The format filter is taking the RGBA (packed) format and converting it to YUVA422 planar.

  



  

  • GCC 8.4

  


  • Ubuntu 18.04

  


  • FFmpeg 4.2

  


  


• FFMPEG - Struggling to find correct input audio codec parameters on macOS

  20 septembre 2024, par Xavi

  I am trying to read my external stereo microphone with ffmpeg within my Qt Windows+macOs application, but I am struggling to obtain consistent correct input codec parameters on macOs. My findings and suspicions so far :

  


  The code I'm using in macOs is the following, where everything returns a successful return code :

  


   avdevice_register_all();
 
 //macOs only, the same code in windows looks for "dshow" 
 const AVInputFormat *inputFormat = av_find_input_format("avfoundation");
 
 AVFormatContext* inputFormatContext;
 avformat_open_input(&inputFormatContext, inputDevice, inputFormat, NULL);

 avformat_find_stream_info(inputFormatContext, NULL);
 
 //... allocate the codec context for the single input stream and
 // copy the parameters from the stream to the context



  


  In my standalone minimal reproducer this always results on the codec ID of the single stream being AV_CODEC_ID_PCM_F32LE, in both macOS and Windows. When I integrate this code in my Qt application on Windows, I get the same result. However, on macOS, most of the times results in the codec id of the stream being AV_CODEC_ID_PCM_S16LE (via AV_CODEC_ID_FIRST_AUDIO) and sometimes AV_CODEC_ID_PCM_F32LE. Both sample formats are supported by my microphone.

  


  AV_CODEC_ID_PCM_F32LE always results in a correct output. AV_CODEC_ID_PCM_S16LE results on buzzy noisy audio slowed down to 0.5x, and If in this case I decode with AV_CODEC_ID_PCM_F32LE instead of copying the codec parameters from the stream, the output sounds correct again.

  


  I am trying to write generic code, so while enforcing the AV_CODEC_ID_PCM_F32LE codec works, I'd rather understand what is happening.

  


  What am I missing ? Is Qt interacting in some way that I can't think of ? I am compiling and linking my own ffmpeg libraries (6.1.1) and not using Qt's ones.