Op ma 31 okt. 2022 om 19:33 schreef Martijn van Beurden <mva...@gmail.com>: > > Op ma 31 okt. 2022 om 17:58 schreef Derek Buitenhuis > <derek.buitenh...@gmail.com>: > > > > It is interesting that the IETF RFC and the Xiph spec disagree on whether > > this is allowed. > > > > The Xiph spec also says the IETF spec is better, and it remains as > historical reference and overview :) > > > The Xiph spec says: > > > > Sample rate in Hz. Though 20 bits are available, the maximum sample > > rate is limited by the > > structure of frame headers to 655350Hz. Also, a value of 0 is invalid. > > > > The RFC just says: > > > > Sample rate in Hz. > > > > The spec as it is on the FLAC website (which is being "preserved") is > wrong. I don't know how this came to be, I think it was at first > poorly worded and later incorrectly fixed. See this commit: > https://github.com/xiph/flac/commit/96534bb5f35eb9c2f6f393dc470625e9c74df1a5 > The text as it was before that commit doesn't make any sense, the text > as it is after the commit is not correct either. > > The issue here is that FLAC has a sample rate in the streaminfo > metadata block, at the very start of the file. That one can > accommodate sample rates up to 2^20-1. The frame headers repeat the > sample rate every frame and can only accommodate up to 655350Hz, but > they can also reference the streaminfo metadata block. Because of the > possibility to reference that 20 bit number, it is possible to store > sample rates up to 1048575Hz. You can see this patch only touches the > encoder: the FFmpeg decoder has already been equipped to deal with > this since its inception in 2004. > > There is some kind of limitation to sample rates above 655350Hz, or > samplerates between 65535Hz and 655350Hz that are not a multiple of 10 > though: a FLAC file with such a sample rate cannot be multicast, > because a decoder receiving a multicast stream does not receive the > streaminfo metadata block, and thus cannot use it to figure out the > correct sample rate. > > Please let me know when this explanation falls short. > > Kind regards, Martijn van Beurden
Hi all, With this email, I would like to renew the attention of the mailing list for this patch. Kind regards, Martijn van Beurden _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
