[Mp4-tech] [Mpeg4 ] [AAC] + mismatch in decoder o/p compared to standard

[Kannan GS Nambiar]

Hi Shreya,
Please go through ISO/IEC 14496- Part4 conformance. This part describes the
conformance criteria that you have
to achieve in terms of LSB and RMS errors. This allows a maximum deviation
between +2 to -2.
Then any two decoder implementations may not be bit exact in all floating
point operations taking place inside
them. Some variables might be in double in one case and the corresponding
variables may be in float in the other case.
Also this depends on some specific implementations of say algorithms for
IMDCT etc. So there is no need to match it bit
by bit. But you have to satisfy the Conformance criteria set by ISO.
Best Regards,
Kannan.
-----Original Message-----
From: Shreya Pathak [mailto:shreya_pathak rediffmail.com]
Sent: Tuesday, October 12, 2023 3:54 PM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] [Mpeg4 ] [AAC] + mismatch in decoder o/p compared to
standard
  Hi,
    I have developed a reference code for Mpeg4 AAC and the decoded output
values when compared with the test vectors there is a mismatch of +/- 1.
i.e, the pcm output values from my reference decoder(floating point code
only)
will be 1 more or less than the pcm values of standard test vectors.The
difference does not exceed 1. I am not getting what the problem is ? If i
compare publicly available code faad from Nero with the standard test
vectors, its also not matching with standard test vectors bit by bit and so
i am not able to debug where there is an error in my reference code.
                    Can u please tell me where I may be wrong ?
Regards
Shreya
On Mon, 11 Oct 2023 Tobias Oelbaum wrote :
>Forwarding a mail from one of my students
>
>Dear experts,
>
>for any of you working with linux/unix/OsX or you just want to test on
>different implementations - here are some tools you may be interested in.
>
>Imagemagick can convert images or series of images to raw yuv (video)
files.
>Syntax: convert x.jpg x.yuv
>http://www.imagemagick.org/
>
>Mplayer can play raw yuv video files.
>Syntax: mplayer -rawvideo on:pal:fps=25 x.yuv
>(http://www.mplayerhq.hu/)
>
>FFMPEG in it's newest version (0.4.9_pre1) can play H.264 files - has CABAC
>but no B-picture support.
>Syntax: ffplay -f h264 x.264
>(http://ffmpeg.sourceforge.net/)
>
>I found them extremely helpful for my work with the reference
>encoder/decoder
>and wanted to contribute.
>
>Regards
>
>Dominic Buchstaller
>Technical University of Munich (TUM) - Germany
>
>P.S.: There should be windows versions for all programs as well.
>
>--------------------------------------------------------------------
>Dipl. Ing. Tobias Oelbaum
>Institute for Data Processing       Lehrstuhl für Datenverarbeitung
>Munich University of Technology     Technische Universität München
>
>EMail: oelbaum tum.de
>Tel:   +49 89 289 23625
>Fax:   +49 89 289 23600
>--------------------------------------------------------------------
>
>
>_______________________________________________
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