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[To: mad-dev@lists.mars.org]
On Fri, 24 May 2002, Rob Leslie wrote:
I'm not sure what units you're using, so to clarify: the number of samples per channel in a frame is generally
32 * MAD_NSBSAMPLES(&frame.header)however after synthesis it is best to use the value in synth.pcm.length instead. (The above expression is wrong if MAD_OPTION_HALFSAMPLERATE is in effect.)
Hmmm, basically I'm looking for the length in bytes. Since the bytes per sample per channel is 2, then we get 64*NBSAMPLES*NCHANNELS. Or so I was thinking.
Since I'm seeking though the file to get the the spot the user has requested, I don't want to be synthing data.
I think decode_frame returns -1 after I call decode_header. I'm not sure if this the the behaviour to expect, or if I'm doing something wrong.
Probably this is due to a real decoding error. If you're seeking around a Layer III stream, the bit reservoir may not have had an opportunity to be refilled, and it's normal to get errors on a few frames in this case.
So since I haven't decoded the last couple of frames, getting an error on the first frame I decode in the middle of the stream is to be expeded? Do you know how many frames back I would at most have to decode before I can correctly decode my target frame? Do I need to synth those frames too?
So basically to do perfect seeking in MP3, I would have to skip though the headers, and keep a point back n number of frames, until I find where I want to be. Reinitalize mad_stream, etc. Seek the file to where my back pointer is indicating. Decode n frames silently, and then start playing at the appropriate place in the nth frame. Whew.
- -- Russell O'Connor roconnor@alumni.uwaterloo.ca http://www.math.berkeley.edu/~roconnor/ ``Later generations will regard set theory as a disease from which one has recovered.'' -- Poincare