On Thu, Aug 25, 2016 at 06:36:45PM -0500, Burt P. wrote: > On Thu, Aug 25, 2016 at 5:46 PM, Jean-Baptiste Kempf <[email protected]> > wrote: > > On 25 Aug, Burt P. wrote : > >> HDCD coding is hidden in some CD audio, but not all, and using it is > >> completely optional. > > > > But you can detect that, cannot you? > > Yes, but it requires scanning the whole audio to know if you will be > using peak extend. > PE requires and 6dB of room at the top for the expanded peaks. > So you have to make two full passes, or just always apply -6dB to all > 16-bit audio in case HDCD/PE appears. > The current implementation does the latter, because we only get the > audio one frame of a few thousand samples at a time. > We need at least one or two seconds, 44100-88200 samples, to know we > will catch an HDCD packet. > There are some HDCD-CDs where only one track had HDCD encoding, > because it was a compilation or something. > In this case, you could have a single file flac+cue being processed, > and not know for 20 minutes into the audio that you need room for peak > extend. > > Audio players can scan ahead, and choose to use HDCD processing or not. > They can even enable-disable per track, or when seeking, by scanning > ahead or behind a couple seconds, without the listener noticing in > most cases. > For avconv/ffmpeg (at least the cli), however, I think it is best left > to the user.
I'm with j-b on this one. If the filter is optional, it will be left out in 99% of cases. It sounds like you are optimizing for a rare edge case and sacrificing ease of use and better quality in 99% of cases for it... Diego _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
