I'm looking all over the Internet for information in regards to calculating the frame length and it's been hard... I was able to successfully calculate the frame length in ms of MPEG-4, AAC, using:
frameLengthMs = mSamplingRate/1000
This works since there is one sample per frame on AAC. For MPEG-1 or MPEG-2 I'm confused. There are 1152 samples per frame, ok, so what do I do with that? :P
Frame sample:
MPEGDecoder(23069): mSamplesPerFrame: 1152
MPEGDecoder(23069): mBitrateIndex: 7
MPEGDecoder(23069): mFrameLength: 314
MPEGDecoder(23069): mSamplingRate: 44100
MPEGDecoder(23069): mMpegAudioVersion 3
MPEGDecoder(23069): mLayerDesc 1
MPEGDecoder(23069): mProtectionBit 1
MPEGDecoder(23069): mBitrateIndex 7
MPEGDecoder(23069): mSamplingRateFreqIndex 0
MPEGDecoder(23069): mPaddingBit 1
MPEGDecoder(23069): mPrivateBit 0
MPEGDecoder(23069): mChannelMode 1
MPEGDecoder(23069): mModeExtension 2
MPEGDecoder(23069): mCopyright 0
MPEGDecoder(23069): mOriginal 1
MPEGDecoder(23069): mEmphasis 0
MPEGDecoder(23069): mBitrate: 96kbps
Answer
The duration of an MPEG audio frame is a function of the sampling rate and the number of samples per frame. The formula is:
frameTimeMs = (1000/SamplingRate) * SamplesPerFrame
In your case this would be
frameTimeMs = (1000/44100) * 1152
Which yields ~26ms per frame. For a different sampling rate you would get a different duration. The key is MPEG audio always represents a fixed number of samples per frame, but the time duration of each sample is dependent on the sampling rate.