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Thread: Amr-codec

  1. #1
    Registered User
    Join Date
    Mar 2003
    Posts
    3

    Amr-codec

    Hi.

    I'm using the amr-codec defined in amrcodec.h in a CMdaAudioRecorderUtility object. I'm trying to use the lowest bitrate mode, but it seems it uses the 12.2kbit/s mode regardless of my constructor parameters. Why is this? Code below:

    // Initiate Audio Recorder
    iRecorder = CMdaAudioRecorderUtility::NewL(*this);

    // temporary storage filename
    iVoiceFileLocation.iName.Append(aFileName);

    iVoiceFileType = new (ELeave) CMdaAudioType;
    iVoiceFileType->iFormat = new (ELeave) TMdaRawAmrClipFormat;
    //The smallest AMR codec type.
    iVoiceFileType->iCodec = new (ELeave) TMdaRawAmrAudioCodec(TMdaRawAmrAudioCodec::EMR475, ETrue);
    iVoiceFileType->iSettings = new (ELeave) TMdaAudioDataSettings;
    iVoiceFileType->iSettings->iSampleRate = 8000;
    iVoiceFileType->iSettings->iChannels = 1;

    if(iRecorder->State() == iRecorder->ENotReady) {
    iRecorder->OpenL(&iVoiceFileLocation, iVoiceFileType->iFormat, iVoiceFileType->iCodec, iVoiceFileType->iSettings);
    BHasBeenConnected = EFalse;

    Why oh why?

    /Johan Axelsson

  2. #2
    Registered User
    Join Date
    Mar 2003
    Posts
    17

    RE: Amr-codec

    "Bit rates of the second-generation cellular standards: GSM EFR (12.2 kbits/s), North American TDMA EFR (7.4 kbits/s), and PDC EFR (6.7 kbits/s)"

    http://www.voiceage.com/AMR/whychoosenarrow.asp


    hope this helps.

  3. #3
    Registered User
    Join Date
    Mar 2003
    Posts
    3

    RE: Amr-codec

    Just as a follow-up; I got the next lowest bitrate to work, the 5.15 kbps mode. And it really makes a difference on the filesizes when compared to 12.2 kbps, and all without any (imho) quality loss.

    The 4.75 just results in the codec using 12.2 which is puzzeling to say the least. ( Yet another undocumented "feature" ).

    /Johan

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