AAC | ADPCM | Convolution | DAFx | FFT | IIR | Mixer | MP3 | MPEG | MPEG-4

Hi,

I'm working on implementing Trick Modes (fast forward, rewind etc) in MP3. In this context, I
need to play audio at higher speeds (2x, 4x). Skipping audio samples distorts the sound (it
sounds very squeaky). Is there any good way of doing this? I'm assuming time warping is what I
need. If yes, could anyone suggest a good article on this?

Thanks,
M
	

(You need to be a member of audiodsp -- send a blank email to audiodsp-subscribe@yahoogroups.com )

As I have not worked on the MP3 but I have the experience in the 
MP4. Well on that bases I am qouating some of the points, may be, it
may help you.

Point 1.

Are you sure that you are intilising the Reader correctly, after
Skipping the x number of bytes ?

Point 2.
Do your application / code is pointing to the correct Chunk Number of the sample, after you
skipp x numbers of bytes ?

Do let us know if you have still face the problem.

BTW are you following the Byte Skip or the Time Stamping to Achive
the to(Foearwd) and fro (rewind) of the audio file?

Regards
Ranjeet
	On Fri, 16 Dec 2005 rajashree_g@raja... wrote :
>Hi,
>I'm working on implementing Trick Modes (fast forward, rewind etc) in MP3. In this context,
I need to play audio at higher speeds (2x, 4x). Skipping audio samples distorts the sound (it
sounds very squeaky).
Is there any good way of doing this? I'm assuming time warping is what I need. If yes, could
anyone suggest a good article on this?
>Thanks,
>M
	

(You need to be a member of audiodsp -- send a blank email to audiodsp-subscribe@yahoogroups.com )

Hi,

if the pitch should change with the tempo, then you are interested in
dynamic sample rate conversion/resampling. This is basically
interpolation and filtering.
If the pitch should remain constant for different tempi, then you are
interested in time stretching/scaling. In this case, look for OLA, PSOLA
or for phase vocoder.
Note that timestretching usually produces more artifacts than resampling.

Cheers,
(a)

rajashree_g@raja... wrote:
> Hi,
> 
> I'm working on implementing Trick Modes (fast forward, rewind etc) in MP3. In this
context, I need to play audio at higher speeds (2x, 4x). Skipping audio samples distorts the
sound (it sounds very squeaky). Is there any good way of doing this? I'm assuming time warping
is what I need. If yes, could anyone suggest a good article on this?
> 
> Thanks,
> M
	

(You need to be a member of audiodsp -- send a blank email to audiodsp-subscribe@yahoogroups.com )