Configuring CMMFCodec for encoding audio to AMR

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Article Metadata

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Compatibility

Platform(s): S60 2nd Edition, FP2 and FP3, S60 3rd Edition

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Article

Keywords: CMMFCodec, AMR

Created: User:Technical writer 2 (19 Oct 2006)

Last edited: hamishwillee (14 Jun 2012)

Overview

Configuring CMMFCodec for encoding audio to AMR.

Description

On S60 2nd Edition, Feature Pack 2 and 3, manual conversion from PCM16-format audio to AMR-NB can be done via the CMMFCodec interface. CMMFCodec also provides a method for configuring the encoder — in this case, specifying the AMR encoding mode (bitrate).

Solution

#include <mmf\plugin\mmfCodecImplementationUIDs.hrh>
 
const TUid KMMFCodecAMREncode = {KAdvancedUidCodecPCM16ToAMR}; // 0x101FAF68
const TUid KUidConfig = {KUidMmfCodecAudioSettings};  // 0x10203622
CMMFCodec* codec = CMMFCodec::NewL(KMMFCodecAMREncode);
TAmrEncParams iEncoderParams;
iEncoderParams.iMode = mode;  // AMR-NB mode between 0...7
iEncoderParams.iDTX = EFalse;
 
// DTX mode
codec->ConfigureL(KUidConfig, (const TDesC8&)iEncoderParams);
 
// proceed to call CMMFCodec::ProcessL()
// see CMMFCodec documentation on SDK Help for more info

The TAmrEncParams class definition is no longer in the SDK. The following definition can be used:

class TAmrEncParams
    {
public:
    inline TAmrEncParams();
public:
    // encoding mode 0-7 (0=MR475,1=MR515,...,7=MR122, default 7)
    TInt iMode;
    // DTX (discontinuous transmission) flag (true/false)
    TInt iDTX;
    };
 
TAmrEncParams::TAmrEncParams() :
    iMode(7), iDTX(0) {}

Note:

• On most current S60 devices, recording/playback and streaming is already done with more efficient hardware (DSP) codecs. These codecs can be taken into use with high-level audio APIs (CMdaAudio[Player|Recorder]Utility, CMdaAudio[Input|Output]Stream), but they cannot be used via the CMMFCodec interface. For some codecs (e.g., AMR-NB) a CMMFCodec implementation is also included for maintaining backward compatibility.}}
• S60 3rd Edition: The above definition for TAmrEncParams works for S60 3rd Edition as well, however the required AMR-NB MMF codec is not included in all S60 3rd Edition phones. The following phone models do include this codec:
  • Nokia 3250
  • Nokia E62
  • Nokia N71
  • Nokia N73
  • Nokia N75
  • Nokia N80
  • Nokia N92
  • Nokia N93
  • Nokia N95
  • Nokia 6290