Re: [mpg123-devel] Help please...

[Clive C. <cl...@wi...>]

Hi Thomas,

> I was about to suggest using mpg123_replace_reader() ... apart from that, the mpg123_decode_frame() API should be somewhat intermixable with mpg123_feed(), but you should be careful with mixing it with mpg123_decode() as that one abstracts over frames. Oh, and you don't need that decode call to get the format. Just do mpg123_getformat(); nowadays that triggers the necessary inital parsing anyway.
>
I did look at mpg123_replace_reader() and decided that it was a little
above my abilities right now.
The way I was doing things meant that the seek didn't work but what I
drew from that was the fact that it worked for the very first seek and
that was interesting.
So..... and this is where you may start to cringe a little.... I
decided that I would create a new mpg123 instance for every seek.....
What!....Yeah.
Here is the code that sits in the scrollbar 'position changed' event
of the application I am writing.
sfifo_flush(fifo);
int ret;
off_t fNum;
size_t bytes;
if(hQplay != NULL)
	mpg123_close(hQplay);
delete hQplay;
hQplay = NULL;
mpg123_init();
hQplay = mpg123_new(NULL, &ret);
if(hQplay == NULL)
	return;
initDecoder(hQplay, mp3Buffer, mp3size, false);
mpg123_seek_frame(hQplay, currentPos - 2, SEEK_SET);
for(int x = 0; x < 8; x++)
{
	mpg123_decode_frame(hQplay, &fNum, &bbuff, &bytes);
	sfifo_write(fifo, bbuff, bytes);
	qDebug() << "Frame Read:" << fNum << "  Length:" << bytes;
}
Error checking!... who needs error checking... ha ha (deal with that later)
This works really well and you can see/hear the result here...

http://youtu.be/lQMja5_awEE

You may notice that I grabbed the same fifo buffer code mpg123 is
using, that works really well.
I have the latency down to under 2 frames, 0.05s.
This does allow a limited slow play that makes it easy to visually and
audibly get to the exact frame you want.

I am also learning a whole lot about how mpg123 works while producing
this application and I am already thinking of adding a function to
mpg123 to allow a forced seek, but that is for later.

I will be interested in any comments from anyone.

Clive
-- 
Infinity: A concept for those who cannot comprehend the big picture.

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