Dear all, I have a wav file that when I try to encode with the FLAC Frontend, I get "ERROR: unsupported format type 3". When I open it with an audio editor I find it is 44100 / 32 bit. I requantized it to 16 bit using the default dither and then compressed it with FLAC to get a 61 Mbyte file (the original was about 347 Mbyte). Obviously, this altered somewhat the quality, although in an indiscernible way (for me, at least). However, as a last attempt, I used Winrar on the original file and to my surprise it was compacted to 79 Mb, only about 33% more than the FLAC version representing a file with half the data. This is interesting since using non-audio compressors usually one seldom gets more than a 10% reduction. Regards, Federico -------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/flac-dev/attachments/20160122/0dd43dff/attachment.htm
Federico Miyara wrote:> > Dear all, > > I have a wav file that when I try to encode with the FLAC Frontend, I > get "ERROR: unsupported format type 3".WAV format 3 is 32 bit IEEE float which is not supported by FLAC.> When I open it with an audio editor I find it is 44100 / 32 bit.32 bit *floating point* values. WAV files can also contain 32 bit (integer) PCM.> I > requantized it to 16 bit using the default dither and then compressed itMaybe requantizing to 24 bit might have made more sense (and 24 bit PCM is handled by FLAC).> However, as a last attempt, I used Winrar on the original file and to my > surprise it was compacted to 79 Mb, only about 33% more than the FLAC > version representing a file with half the data.If the orignal 32 bit IEEE float file had been normalized so that all sample values are between -1.0 and +1.0 then the exponent part of each floating point value (8 bits out of 32 bits) would have been identical resulting in a very significant opportunity for a data compressor like WinRAR to do it's work. A much better (fairer?) comparison would be to compare how WinRAR compresses a 24 bit PCM WAV file in comparison to FLAC. Erik -- ---------------------------------------------------------------------- Erik de Castro Lopo http://www.mega-nerd.com/
Erik, The file indeed reached +/- 1 (one channel is the output of a magnetic switched device, the audio signal is not strictly on-off but it has a characteristic pattern that saturates). I performed the test you've suggested. I used Audacity to convert 32-float to 24-signed. The original size of 347 Mb reduced to 260 Mb, the expected 3/4 reduction. Then I compressed it with FLAC, getting a 120 Mb file, and with Winrar, getting a 54 Mb file. However this may be an anomalous case, since I've tested other (16 bit) audio files and FLAC outperforms RAR. Regards, Federico On 22/01/2016 3:09, Erik de Castro Lopo wrote:> Federico Miyara wrote: > >> Dear all, >> >> I have a wav file that when I try to encode with the FLAC Frontend, I >> get "ERROR: unsupported format type 3". > WAV format 3 is 32 bit IEEE float which is not supported by FLAC. > >> When I open it with an audio editor I find it is 44100 / 32 bit. > 32 bit *floating point* values. WAV files can also contain 32 bit (integer) > PCM. > >> I >> requantized it to 16 bit using the default dither and then compressed it > Maybe requantizing to 24 bit might have made more sense (and 24 bit PCM > is handled by FLAC). > >> However, as a last attempt, I used Winrar on the original file and to my >> surprise it was compacted to 79 Mb, only about 33% more than the FLAC >> version representing a file with half the data. > If the orignal 32 bit IEEE float file had been normalized so that all > sample values are between -1.0 and +1.0 then the exponent part of each > floating point value (8 bits out of 32 bits) would have been identical > resulting in a very significant opportunity for a data compressor like > WinRAR to do it's work. > > A much better (fairer?) comparison would be to compare how WinRAR compresses > a 24 bit PCM WAV file in comparison to FLAC. > > Erik-------------- next part -------------- An HTML attachment was scrubbed... URL: http://lists.xiph.org/pipermail/flac-dev/attachments/20160123/914d1efc/attachment.htm
On 22 January 2016 at 07:09, Erik de Castro Lopo <mle+la at mega-nerd.com> wrote:>> However, as a last attempt, I used Winrar on the original file and to my >> surprise it was compacted to 79 Mb, only about 33% more than the FLAC >> version representing a file with half the data. > > If the orignal 32 bit IEEE float file had been normalized so that all > sample values are between -1.0 and +1.0 then the exponent part of each > floating point value (8 bits out of 32 bits) would have been identical > resulting in a very significant opportunity for a data compressor like > WinRAR to do it's work.IIRC WinRAR does not use one single general compression algorithm for all file types but has its own specialised lossless compression algorithm for wav files. Not quite as good as flac apparently, but still. Riggs