Recherche avancée

Sur d’autres sites (5493)

• How to use libavformat for a separate encoder ?

  5 juin 2014, par Brendon Tsai

  I’ve build a encoder based on the sample of QUALCOMM, which captures the video and compresses it into h264 file. I am using Android 4.2.2. Now I want to add a mp4 muxer into this encoder(actually, just video will be fine, I don’t need audio).

  I want to use FFMpeg. But after I read the example, I found out that the muxer was using the encoder of FFMpeg. I don’t know how to use the muxer part for another encoder.

  I’ve read this post, but I don’t understand how the code provide video stream to the muxer. I think that mainly because I don’t understand these code :

  AVCodecContext * strmCodec = oFmtCtx->streams[0]->codec;
  
  
  
  // Fill the required properties for codec context.
  
  // *from the documentation:
  
  // *The user sets codec information, the muxer writes it to the output.
  
  // *Mandatory fields as specified in AVCodecContext
  
  // *documentation must be set even if this AVCodecContext is
  
  // *not actually used for encoding.
  
  my_tune_codec(strmCodec); 

  Can anyone give me a hint ? Thank you !

• ffmpeg : Infinite amount of filters/crossfading dynamic playlist

  30 juillet 2019, par MaPePeR

  I want to use ffmpeg to play a dynamic playlist infinitely. The idea is, that an external command/script is executed to request the path to the next file (using the predicted start-time of the file as an argument) and continue playing files infinitely.

  From the answer to "Using FFMPEG to stream continuously videos files to a RTMP server" i learned, that i need to write a custom demuxer, that is similar to the concat demuxer. The problem arises from the fact, that i want to crossfade between the audio files and from my understanding of the demuxer i would have to implement that functionality into the demuxer itself to be able to do it, because a demuxer can only produce one (or a finite number) audio output stream and you need two to use the acrossfade-filter.

  So i would have to set up the filter graph like this :

  file1 --------------------------------*-->| cross | ---->more filters ---> Output
  
  file2 -----------------*-->| cross |----->| fade  |
  
  file3 --*-->| cross |----->| fade  |
  
        ... ->| fade  |

  Using an infinite number of crossfade-filters.

  Also i would really like to pre-filter(*, e.g. silenceremove) the audio files before cross-fading, which makes it even more complicated and the "implement everything in the demuxer"-approach even worse.

  My current solution would be to implement a custom demuxer that alternates between two output streams and does the prefiltering internally as well as an input-alternating crossfade filter like this :

  files -> | alternating |----->| alternating | ----> more filters--->
  
           |   demuxer*  |----->|  crossfade  |

  The problem i see with this approach is that i would need to send multiple EOF-terminated files from the demuxer to the crossfade-filter and i don’t know if that is even possible/allowed when using the standard ffmpeg functions like ff_request_frame.

  Can you tell me if this approach is feasible or do you have a better solution to this problem or any idea that would make this easier ?

• Conan OpenCV with FFMPEG

  20 avril 2020, par Bixilein

  For my project I would like to use OpenCV from conan. For my application I need OpenCV with the FFMPEG option enabled.

  



  I tried to do conan install opencv/4.1.1@conan/stable -o ffmpeg=True -b missing but I got a lot of compiler errors with undefined references. All the errors are related to FFMPEG.

  



  In the conanfile of opencv ffmpeg/4.2@bincrafters/stable is listed as a requirement. I tried to just install fmpeg/4.2@bincrafters/stable but I got the same errors. After some experimenting, I found out that fmpeg/4.2.1@bincrafters/stable is working on my system.

  



  Therefore, I wanted to use this working version of ffmpeg for OpenCV. In the conan-cache I changed the conanfile for OpenCV to take ffmpeg/4.2.1 and then tried again to install OpenCV. This time everything build without error and a new hash was created.

  



  Now I wanted to use this OpenCV in my project. But when I try to build my project, I get an error. The problem seems to be that conan is looking for a specific hash and because I changed the requirements in the conanfile of OpenCV the hash is now different. The hash of my local OpenCV is 91716d2466cac1ff5c91a7b802ce2d69b84cc798, but when I try to build my project it is looking for a different hash. (opencv/4.1.1@conan/stable:7234edbe78e5002a4384cde97bca91abd732a248 - Missing)

  



  I am new to conan and therefore I do not know if the approach I took so far is acceptable. I appreciate every feedback on how to approach this problem.