Re: recording bugs (Was: [Protux-devel] color experimentation on BusMonitor)

[Martin Herren]

On Mon, 13 Jan 2003 23:31:43 +0000
Luciano Giordana <address@hidden> wrote:

> How zooming works ( please add this into SPECIFICATIONS file documentation 
> purposes)
> 
> 1)  what means 1:n
> 
> each 1 peak show (a red line 1 pixel wide), n are scanned, and the maximum of 
> them is the most representative
> 
> 2) from 1:1 to 1:64, the data is scanned directly from the audio file. This 
> is possible because considering a standard video screen of 1024 pixels
> 
> the maximum samples read from the file will be 64*1024*2 (2 channels), which 
> is a low data quantity even for the slowest hard disks today
> 
> 3) from 1:64 on, a Peak image is pre-built (peak class) the "most 
> representatives" peaks are stored in peak "buffers", so when the clip must
> be drawn, instead of scanning all samples from the files, the Peak class 
> gives the pre-scanned peaks from the buffers. These buffers are
> pre-saved in .peak files so they can be fastly load .
> 
> 4) zooming is done by redrawing the clips. The clips, when redraw, re-read 
> the peak buffers for the current zoom factor (1:64, 1:128, and so on...
> 
> 5) The current horizontal zoom factor is controlled by the variable hzoom in 
> Song. It goes from 0 to 32 , corresponding to the factores 1:1 ... 1:65536
> 
> The increment is not x2.  The complete sequence of factores are 1:x where x 
> is :
> 
>  1,    2,    4,     6,     8,    12,    16,    20, 24,   32,   48,    64,    
> 64,    96,   128,   192, 256,  384,  512,   768,  1024,  1536,  2048,  3072, 
> 4096, 6144, 8192, 12288, 16384, 24576, 32768, 65536
> 
> 
> 6) scrolling is done by changing the variable firstBlock at Song class. and 
> recreating the tracks
> 
> 7) There are 2 important functions in Song that converts from a "X" point (a 
> x coordinate in the screen) to the equivalent audio block position
> the "block" position is defined by
> 
> blockpos = fileposition / (channels*(bitdepth/8)
> 
> which means the position of a pair of samples for a stereo file or the 
> position of a sample for a mono file
> 
> 
> so, the two functions are 
> 
> int Song::block_to_xpos(long long block)
> 
> long long Song::xpos_to_block(int xpos)
> 
> 
> By using these functions a clip "knows" where to draw the peak graphics for a 
> pair of samples by getting a corresponded xpos for those samples' block 
> positions
> 
> 
> 
> I hope that these informations help to understand zooming, clip drawing and 
> scrolling
> 
> L

thanks... didn't have time to get more into it yet, but this will definitively 
help !


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Martin Herren                             +41 (0)79 746 57 83
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