avformat_open_input cannot open a file with raw opus audio data

Question

I have a problem when trying to open a binary file containing raw audio data in opus format. When I try to open this file, the library returns an error: Unknown input format: opus.

How can I open this file ?

I need to open it and write all the raw audio data to an audio container. I understand that the opus format is intended only for encoding. I realized this using command:

$ ffmpeg -formats | grep Opus

ffmpeg version 3.4.4 Copyright (c) 2000-2018 the FFmpeg developers
  E opus Ogg Opus # For only encoding

Then what format should I use to open this file ? With ogg ? I tried, but there are also problems with opening the outgoing file. I provide the code that shows only the necessary part to open the file:

int main(int argc, char *argv[])
{
    // ...

    av_register_all();

    AVFormatContext *iFrmCtx = nullptr;
    AVFormatContext *oFrmCtx = nullptr;
    AVPacket packet;

    const char *iFilename = "opus.bin"; // Raw audio data with `opus` format
    const char *oFilename = "opus.mka"; // Audio file with `opus` audio format

    AVDictionary* frmOpts = nullptr;
    const qint32 smpRateErrorCode = av_dict_set_int(&frmOpts, "sample_rate", 8000,  0);
    const qint32 bitRateErrorCode = av_dict_set_int(&frmOpts, "bit_rate",    64000, 0);
    const qint32 channelErrorCode = av_dict_set_int(&frmOpts, "channels",    2,     0);
    if (smpRateErrorCode < 0 ||
            bitRateErrorCode < 0 ||
                channelErrorCode < 0) {
        return EXIT_FAILURE;
    }

    AVInputFormat *iFrm = av_find_input_format("opus"); // Error: Unknown input format
    if (iFrm == nullptr) {
        av_dict_free(&frmOpts);
        return EXIT_FAILURE;
    }

    qint32 ret = 0;
    if ((ret = avformat_open_input(&iFrmCtx, iFilename, iFrm, &frmOpts)) < 0) {
        av_dict_free(&frmOpts);
        return EXIT_FAILURE;
    }

    // We're doing something...
}

Answer 1

As said before Opus is not self-delimiting, it needs a container. and since you got the raw data from rtp payload, and the opus codecs is a dynamic codecs (with dynamic payload size) you can't use ffmpeg AVFormatContext to read raw data from the file.

But you can work around this issue and instead of using (av_read_frame) to fill the AVPacket to decode them you can manually fill the AVPacket data and size and then push it to the decoder.

note that you should also update the pts and dts for each AVPacket .