On Mar 4, 2013, at 14:39, Timothy B. Terriberry wrote: > Erik de Castro Lopo wrote: >> Err, thats a link to a post talking about flac's WAV reader being >> limited >> to 4Gig files. Problem is, *all* WAV files greater than 4Gig are >> mal-formed. >> Due to limitations in the way WAV files are specified, no valid >> WAV file >> can ever be over 4Gig. > > And most don't work over 2 GB. The solution we (Xiph) have used in > other > projects (opusenc, oggenc) is to treat sizes over ~2 GB as meaning > "Just > keep reading until EOF." See wav_open() audio-in.c in opus-tools. It > turns out you need to use slightly less than 2 GB for the limit to > handle the output of some tools. We also provide an --ignorelength > option to request this behavior regardless of the length in the header > (which lets it work with tools that just truncate the size to 32 > bits).
That's an awful "solution" waiting for errors to be introduced into what might otherwise be valid files. There is no way for a RIFF/WAVE to exceed 4 GB because all chunks must be enclosed within a global chunk, which is limited to a 32-bit size. I've seen audio software introduce a horrendous glitch in the audio by interpreting the ID3 data as part of the audio chunk. Under no circumstances should a lossless encoder like FLAC accept a malformed audio file and blindly treat potentially random data as audio. Case in point: I just downloaded a 24-bit WAV that was truncated without warning. Thankfully, when I tried to compress it with FLAC, I received a warning that the file was too short. That error prompted me to download the file a second time, and I got the whole thing on the second try. Lossless is useless if you don't even know that the original file is missing pieces. The proper solution is to use POSIX API that support 32-bit unsigned file offsets instead of the older 32-bit signed offsets (which supposedly still have merit because they allow seeking backwards from the current position). There should be no valid reason to "just keep reading until EOF" in a format like WAV that has two, redundant chunk sizes defined (the 'RIFF'/'WAVE' chunk encloses all other chunks, the 'data' chunk encloses all valid audio samples). Brian Willoughby Sound Consulting _______________________________________________ flac-dev mailing list flac-dev@xiph.org http://lists.xiph.org/mailman/listinfo/flac-dev
