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• avdevice : add info about media types(s) to AVDeviceInfo

  21 décembre 2021, par Diederick Niehorster

  avdevice : add info about media types(s) to AVDeviceInfo
  An avdevice, regardless of whether its category says its an audio or
  
  video device, may provide access to devices providing different media
  
  types, or even single devices providing multiple media types. Also, some
  
  devices may provide no media types. dshow is an example encompassing all
  
  of these cases. Users should be provided with this information, so
  
  AVDeviceInfo is extended to provide it.
  Bump avdevice version
  Signed-off-by : Diederick Niehorster <dcnieho@gmail.com>
  
  Reviewed-by : Roger Pack <rogerdpack2@gmail.com>
  

  • [DH] libavdevice/avdevice.c
  • [DH] libavdevice/avdevice.h
  • [DH] libavdevice/version.h

• avformat_write_header return error code when trying to write video with G711U audio avi file

  10 décembre 2024, par denn

  I'm trying to make an avi file from a video/audio stream. When audio is AAC it works fine. But I cannot pack G711U audio.

  


    av_register_all();
  avcodec_register_all();
  av_log_set_callback(nullptr);

  av_format_context_ = avformat_alloc_context();
  if (!av_format_context_)
  {
    std::string error_msg = "Failed to allocate avformat context";
    log_->Error(error_msg);
    throw std::runtime_error(error_msg.c_str());
  }

  av_format_context_->oformat = av_guess_format("mp4", filename.c_str(), NULL);
  strcpy(av_format_context_->filename, filename.c_str());

  AVCodec* codec = avcodec_find_encoder(AV_CODEC_ID_PCM_MULAW);
  av_format_context_->oformat->audio_codec = codec->id;

  audio_stream_ = avformat_new_stream(av_format_context_, codec);
  if (audio_stream_ == nullptr)
  {
    log_->Error("Can not create audiostream.");
    return false;
  }

  AVCodecContext& codec_context = *audio_stream_->codec;
  if (avcodec_copy_context(audio_stream_->codec, av_format_context_->streams[1]->codec) != 0)
  {
    log_->Error("Failed to Copy Context");
    return false;
  }

  audio_stream_->time_base = { 1, codec_context.sample_rate };

  if (av_format_context_->oformat->flags & AVFMT_GLOBALHEADER)
    codec_context.flags |= AV_CODEC_FLAG_GLOBAL_HEADER;

  log_->Info("Init output {}", filename);
  av_dump_format(av_format_context_, 0, filename.c_str(), 1);

  int ret = avio_open(&av_format_context_->pb, filename.c_str(), AVIO_FLAG_WRITE);
  if (ret < 0)
  {
    log_->Error("Can not open file for writing.");
    return false;
  }

  ret = avformat_write_header(av_format_context_, NULL);
  if (ret < 0)
  {
    log_->Error("Can not write header.");
    return false;
  }



  


  Here avformat_write_header() returns -22. What's wrong here ? Which data should I supply to this function ?

  


• Python : How to decode a mp3 chunk into PCM samples ?

  30 mars 2021, par Bendzko

  I'm trying to catch chunks of an mp3 webstream and decoding them into PCM samples for signal processing. I tried to catch the audio via requests and io.BytesIO to save the data as .wav file.

  



  I have to convert the mp3 data to wav data, but I don't know how. (My goal is not to record a .wav file, i am just doing this to test the algorithm.)

  



  I found the pymedia lib, but it is very old (last commit in 2006), using python 2.7 and for me not installable.

  



  Maybe it is possible with ffmpeg-python, but I have just seen examples using files as input and output.

  



  Here's my code :

  



  import requests
import io
import soundfile as sf
import struct
import wave
import numpy as np


def main():
    stream_url = r'http://dg-wdr-http-dus-dtag-cdn.cast.addradio.de/wdr/1live/diggi/mp3/128/stream.mp3'
    r = requests.get(stream_url, stream=True)
    sample_array = []
    try:
        for block in r.iter_content(1024):
            data, samplerate = sf.read(io.BytesIO(block), format="RAW", channels=2, samplerate=44100, subtype='FLOAT',
                                       dtype='float32')
            sample_array = np.append(sample_array, data)

    except KeyboardInterrupt:
        print("...saving")
        obj = wave.open('sounds/stream1.wav', 'w')
        obj.setnchannels(1)  # mono
        obj.setsampwidth(2)  # bytes
        obj.setframerate(44100)

        data_max = np.nanmax(abs(sample_array))

        # fill WAV with samples from sample_array
        for sample in sample_array:
            if (np.isnan(sample) or np.isnan(32760 * sample / data_max)) is True:
                continue
            try:
                value = int(32760 * sample / data_max)  # normalization INT16
            except ValueError:
                value = 1
            finally:
                data = struct.pack('code>

  



  Do you have an idea how to handle this problem ?