Re: Starting/stopping decoding of same stream

On Mar 26, 2004, at 4:54 AM, Erik Jälevik wrote:
> I need to stop and start decoding the same stream at regular intervals 
> depending on the PCM buffer size. So at stage 3 above, I call 
> mad_decoder_run on the properly initialised decoder, and in the output 
> callback, I return MAD_FLOW_STOP when I've been given enough frames to 
> fill the buffer.
>
> Up until now everything's fine. But, it seems that the next time the 
> buffer gets empty and I restart by calling mad_decoder_run again on 
> the same decoder, the decoder doesn't remember the input last given to 
> it by the input callback. So the first thing it does is call the input 
> callback for more input. The mad_stream->next_frame passed into the 
> input callback is always 0 after a restart.
>
> This causes problems because the input callback has no way of knowing 
> how far into the previous chunk MAD has decoded. Is there any way to 
> find this out from the decoder itself?

Only if you record the position yourself, perhaps in the filter 
callback. But you will encounter a more serious problem, which is that 
all the other decoder state (synthesis filterbank, Layer III overlap, 
etc.) is destroyed when mad_decoder_run() returns.

> I haven't looked at the low-level API yet, will I maybe need to use 
> that to achieve what I want?

I think you will indeed. It's not terribly difficult; for some 
guidance, have a look at Bertrand Petit's madlld:

     http://www.bsd-dk.dk/%7Eelrond/audio/madlld/

Cheers,

-- 
Rob Leslie
[email protected]