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Topic: Can AAC change sampling rate w/in file/stream? Do decoders support it? (Read 6620 times) previous topic - next topic

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  • poochi
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Can AAC change sampling rate w/in file/stream? Do decoders support it?
AAC encoded data can come in many container formats . Like Mp4 ,adts etc., . In any of these are the sampling rates allowed to change inbetween  a file ?If so are there any decoders which support it ?

  • saratoga
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Can AAC change sampling rate w/in file/stream? Do decoders support it?
Reply #1
The sampling rate is fixed at encode time.

However for aac-he files a decoder can optionally downsample by 2 if it does not support he. This is because he files are actually encoded at half sample rate and then upsampled by the decoder to the original rate.

  • Rescator
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Can AAC change sampling rate w/in file/stream? Do decoders support it?
Reply #2
Also note that lossy encoders only encode as little as possible, so even if a sample rate was 192KHz, but there was only audio (or a lowpass filter) under 16000 Hz then that would be effectively the same as a sampling rate of 32KHz.