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• question regarding ffmpeg webcam stream (RTMP)

  7 janvier 2021, par J Hwang

  I am a novice if you will regarding FFMPEG.
I was tasked with creating a Windows-based C++ project that takes a live webcam stream, does the necessary decoding and encoding, and sends it via RTMP to a server.
The constraints were that the output format be "flv" due to the design of the server end and that it take both audio and video input. Quality of the stream isn't that much of an issue as long as the audio doesn't desync too much from the video.

  


  I drew on the prior works of https://github.com/leixiaohua1020 in simplest_ffmpeg_streamer and simplest_ffmpeg_device.

  


  Specifically, I tried to mesh together the logic behind the readcamera project to provide an input stream and send it to an output address using the streamer part that previously took a local flv video as input.

  


  However, I ran into some problems.

  


  First of all, I know vfwcap is very much outdated but it seems dshow has some problems with the input part as well as the output part so I'm opting for whichever works first.

  


  Second of all, I don't really understand how to set the codec for the input. The input is using rawvideo by default and I tried to add settings as shown.
pFormatCtx->video_codec_id = AV_CODEC_ID_MPEG4;
However, none of the even slightly relevant codec settings seemed to work. All showed the same error message in the vfwcap error message image below.

  


  I would very much appreciate any pointers on achieving 1. change of codec in input stage 2. fixes for the dshow case

  


  I have put the full code up on github with the appropriate mentions.
https://github.com/luorix1/ffmpeg

  


  error message_dshow

  


  error message_vfwcap

  


• FFMpeg Question about paket pts, dts and duration parameters

  27 avril 2020, par Denis Gottardello

  According with the remuxing.c example I have using the flollowing 3 lines of code :

  



  Packet.pts= av_rescale_q_rnd(Packet.pts, pAVStreamIn->time_base, pAVStreamOut->time_base, static_cast<avrounding>(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));&#xA;Packet.dts= av_rescale_q_rnd(Packet.dts, pAVStreamIn->time_base, pAVStreamOut->time_base, static_cast<avrounding>(AV_ROUND_NEAR_INF | AV_ROUND_PASS_MINMAX));&#xA;Packet.duration= av_rescale_q(Packet.duration, pAVStreamIn->time_base, pAVStreamOut->time_base);&#xA;</avrounding></avrounding>

  



  The code works but not using an rtsp camera as source. I obtain an error at av_interleaved_write_frame function.
Please have a look at the following log report :

  



  AudioIndex Packet.pts: 0, Packet.dts: 0, Packet.duration: 160
AudioIndex Packet.pts: 120, Packet.dts: 120, Packet.duration: 160  
AudioIndex Packet.pts: 312, Packet.dts: 312, Packet.duration: 160
AudioIndex Packet.pts: 432, Packet.dts: 432, Packet.duration: 160
AudioIndex Packet.pts: 632, Packet.dts: 632, Packet.duration: 160
AudioIndex Packet.pts: 752, Packet.dts: 752, Packet.duration: 160
AudioIndex Packet.pts: 952, Packet.dts: 952, Packet.duration: 160
AudioIndex Packet.pts: 1072, Packet.dts: 1072, Packet.duration: 160
AudioIndex Packet.pts: 1272, Packet.dts: 1272, Packet.duration: 160
AudioIndex Packet.pts: 1392, Packet.dts: 1392, Packet.duration: 160
AudioIndex Packet.pts: 1592, Packet.dts: 1592, Packet.duration: 160
AudioIndex Packet.pts: 1712, Packet.dts: 1712, Packet.duration: 160
VideoIndex Packet.pts: 9223372036854775808, Packet.dts: 9223372036854775808, Packet.duration: 0


  



  As you can see the pts, dts, duration parameters relative to audio stream is ok, the video parameters abolutally not.
How can I do to rewrite the video parameters ?
Can anyone explain ?

  


• FFMPEG reduce dynamic range (VLC port question)

  14 mars 2020, par H3rdell

  Is there a way to do the exactly same thing as the image below (VLC) but using FFMPEG ? I want it with FFMPEG to automate some jobs with batch files.

  

  In VLC, alongside the settings in the above image, I also enable the Dynamic Range Compressor.

  

  My settings for the compressor filter in VLC are :

  • RMS/PEAK : 0
  • ATTACK : 15ms
  • RELEASE : 300ms
  • THRESHOLD : -25dB
  • COMPRESSION RATIO : 20.0 to 1
  • KNEE RADIUS : 1.0dB
  • MAKEUP GAIN : 15.0dB

  Thanks in advance.