technosaurus / pdmp3 Goto Github PK

Lots of room for improvement.

1. Floating point constants should be 0.0f (float) vs. 0.0 (double) for faster float ops
2. slow math ops like sin, cos & pow should be offloaded to lookup tables where possible
   a. ) 1 version with init code to reduce binary size at the cost of startup time
   b. ) another version with static const lookup tables for faster startup at the cost of size
   c. ) some areas just need the math simplified for easier calculation
   multiply by precalculated 1/float is faster than divide by float
   some things need ops rearranged so constants can be merged and separated from variables
3. unwind some loops into return/initialization (less memcpy lookalikes)
4. functions should take pointers instead of using globals and some_func(void)

It looks like variables is_ratio_l and is_ratio_r are just assigned but not used anywhere.

The given sfb can be 21 or 12, which exceeds as an index of g_main_data.scalefac_l[gr][ch] or g_main_data.scalefac_s[gr][ch].

I tested with an MP3 file at http://publicdomain4u.com/new-sound-for-an-old-baseball-classic

https://github.com/technosaurus/PDMP3/blob/master/pdmp3.c#L569

I guess +2261 should be +2773.

https://github.com/technosaurus/PDMP3/blob/master/pdmp3.c#L1920

I'm not confident but the index for count1 should be inverted? So the above line should be

max_pos = id->g_side_info.count1[gr][!(id->g_side_info.count1[gr][0] > id->g_side_info.count1[gr][1])];

I got the library to work, by reverting to the older commit before the streaming functions were added.

i can decode an MP3 ok, unfortuantely there are noticable 'scratchy' type sounds present in the output. this is in comparison to audacity where the quality is much better.

it would be great if this could be fixed. otherwise. the library is not usable in a professional application, and i would hope others looking for a non-LGPL decoder do not waste a day setting it up as i did.

I dumped the raw output to a file and now I want to convert this file to .wav with ffmpeg:

ffmpeg.exe -f s8 -ar 44000 -ac 2 -i result.txt -ar 44100 -ac 1 out1.wav

The length (in seconds) of the output is valid but instead of sound I can only hear clicking.