[Mp4-tech][audio] Mpeg4 AAC: why to skip frame

[Shreya Pathak]

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Hi,
   Thanks for the reply.I was testing my Mpeg4 AAC Decoder and 
  i found that for some test vectors the output is of same length as the test vector, but for some test vectors the length is not same.
 If I skip the first frame or skip first 2 frames, the output length is same as test vector. But This skipping of frames is not fixed for all the test vectors.For some skipping one frame gives correct length and for some without skipping and some skipping 2 frames.
So please can you suggest me where i am wrong ?
Regards
Shreya
On Wed, 29 Sep 2023 DDomazet wrote :
>HI,
>
> >Hi,
> >In Mpeg4 AAC decoder publicly available code from Nero i.e FAAC,
> >in file decoder.c
> >if (hDecoder->frame <= 1)
> >hInfo->samples = 0;
> >They are skipping the first frame.
> >I didn't get why they are skipping the first frame.
>
>BECAUSE YOU NEED TWO ENCODED FRAMES
>IN ORDER TO PRODUCE ONE VALID OUTPUT FRAME.
>
>FOR DIAGRAMS BELOW:
>M=1024
>t - time samples after inverse MDCT transformation
>f - frequencies after MDCT transformation
>
>DECODING:
>
>
>
>ENCODING:
>M=1024
>
>
>
> >Regards
> >Shreya
>
>HOPE THIS HELPS,
>DANIEL
>