The Moving Picture Experts Group

Is stream splicing or "break-in" supported in MPEG-2 AAC?


In MPEG-2 AAC Low Complexity and MPEG-2 AAC SSR modes, the prediction tools are not used, so break-in support is the same as that for MPEG-1 audio. For MPEG-2 AAC Main Profile, when prediction is enabled, break-ins are a little tricker, as break-ins can only occur when there is a predictor reset across all frequency bands. This only happens in case of æattacksÆ when the bitstream switches from long to short windows, so the easiest way to break in a main profile bitstream is to start with a short block. For long windows the predictors are reset in a frequency-cyclic way, which may require up to 240 frames before all predictors are reset. So if you break in with long windows, some distortions might appear in the first few frames. The Encoder can be set-up to reset the predictors more frequently which reduces the required number of frames needed before all predictors are reset.