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. This is just my opinion. Maybe libav does prefer a regular decoder. -- Burt _______________________________________________ libav-devel mailing list [email protected] https://lists.libav.org/mailman/listinfo/libav-devel
