Hello. I just added 24 bit support to CRAM and noticed that 24 bit data isn't compressing much, if at all. I saw a recent thread on this list concerning this same issue.
http://lists.xiph.org/pipermail/flac-dev/2006-July/001907.html I ran some tests using the command line 'flac' program and also experienced rather poor results. When doing a 'flac -a' many of the files have VERBATIM FLAC chunks in them, as the above thread mentions also. Any ideas on what could be causing this? One test I did was to take one file that performed rather poorly and convert it to 16 bit and then back to 24 bit again (verified with a hex editor that LSBytes were 0s). Here were the results: Original 24 bit: 192812 -> 197026 bytes = 102% (got bigger) 16 bit: 128556 -> 97725 bytes = 76% 24 -> 16 -> 24: 192812 -> 183695 bytes = 95.2% An interesting note is that compressing the 16 MS bits and encoding the LS 8 bits verbatim would be smaller. Below are some results for files I compressed with flac at 24 bit and 16 bit (converted with ecasound). I'll poke around in the FLAC code a bit to see if I can find anything, but I thought I'd post here to see if anyone has a better idea of what might be wrong. Best regards, Josh Green 24 bit options: -P 4096 -b 4608 -m -l 8 -q 0 -r 3,3 Bees1_clip01.wav: wrote 243159 bytes, ratio=0.945 Bees1_clip02.wav: wrote 319382 bytes, ratio=0.782 Bees2_clip01.wav: wrote 535266 bytes, ratio=1.007 Bees3_clip01.wav: wrote 538943 bytes, ratio=0.805 Bees3_clip02.wav: wrote 356050 bytes, ratio=0.865 Bees3_clip03.wav: wrote 202738 bytes, ratio=0.758 Bees3_clip04.wav: wrote 180798 bytes, ratio=0.774 Bees3_clip05.wav: wrote 348487 bytes, ratio=0.782 Bees3_clip06.wav: wrote 246837 bytes, ratio=0.833 Bees4_clip01.wav: wrote 397719 bytes, ratio=1.003 Bees4_clip02.wav: wrote 239811 bytes, ratio=0.908 Bees4_clip03.wav: wrote 367556 bytes, ratio=1.005 Cricket01.wav: wrote 243255 bytes, ratio=1.015 Cricket02.wav: wrote 197026 bytes, ratio=1.022 GrassHopper_clip01.wav: wrote 768673 bytes, ratio=1.001 GrassHopper_clip02.wav: wrote 638097 bytes, ratio=0.987 GrassHopper_clip03.wav: wrote 557699 bytes, ratio=0.997 GrassHopper_clip04.wav: wrote 568383 bytes, ratio=1.005 GrassHopper_clip05.wav: wrote 1459159 bytes, ratio=0.945 SeedPod1.wav: wrote 259027 bytes, ratio=1.005 SeedPod2.wav: wrote 289343 bytes, ratio=0.999 SeedPod3.wav: wrote 273867 bytes, ratio=0.985 16 bit options: -P 4096 -b 4608 -m -l 8 -q 0 -r 3,3 Bees1_clip01_16.wav: wrote 116837 bytes, ratio=0.681 Bees1_clip02_16.wav: wrote 165013 bytes, ratio=0.606 Bees2_clip01_16.wav: wrote 261264 bytes, ratio=0.737 Bees3_clip01_16.wav: wrote 275022 bytes, ratio=0.616 Bees3_clip02_16.wav: wrote 176597 bytes, ratio=0.643 Bees3_clip03_16.wav: wrote 106485 bytes, ratio=0.597 Bees3_clip04_16.wav: wrote 94403 bytes, ratio=0.606 Bees3_clip05_16.wav: wrote 180244 bytes, ratio=0.607 Bees3_clip06_16.wav: wrote 125787 bytes, ratio=0.636 Bees4_clip01_16.wav: wrote 186186 bytes, ratio=0.705 Bees4_clip02_16.wav: wrote 117756 bytes, ratio=0.668 Bees4_clip03_16.wav: wrote 173618 bytes, ratio=0.712 Cricket01_16.wav: wrote 123631 bytes, ratio=0.774 Cricket02_16.wav: wrote 97725 bytes, ratio=0.760 GrassHopper_clip01_16.wav: wrote 414547 bytes, ratio=0.810 GrassHopper_clip02_16.wav: wrote 350511 bytes, ratio=0.813 GrassHopper_clip03_16.wav: wrote 311311 bytes, ratio=0.835 GrassHopper_clip04_16.wav: wrote 312618 bytes, ratio=0.829 GrassHopper_clip05_16.wav: wrote 739746 bytes, ratio=0.718 SeedPod1_16.wav: wrote 134188 bytes, ratio=0.781 SeedPod2_16.wav: wrote 149471 bytes, ratio=0.774 SeedPod3_16.wav: wrote 144464 bytes, ratio=0.779 _______________________________________________ Flac-dev mailing list [email protected] http://lists.xiph.org/mailman/listinfo/flac-dev
