encode HDCD feature

[Adrian Zaugg]

ffmpeg is able to decode HDCD which is great. There are also use cases where encoding HDCD would be useful, so I request to implement that feature, please.

HDCD is protected by US patent 5479168 (1) and maybe others. It seems to me, that this patent has expired or will expire soon (I don't know anything of patent law). If that patent really has expired, it would be nice to see that feature in ffmpeg.

There are some scenarios, where HDCD encoding would be useful:

• producing your own CDs with HDCD support
• drive a DAC with HDCD support not able to process more than 16 resp. 20bits (like some Burr-Brown from the 90's) - this would enhance the music quality coming from high res sources on those devices
• ..and maybe others like stream HDCD encoded to reduce bandwith or reduce file size without loosing quality in certain circumstances

There is still a lot of equipment out there that is HDCD enabled, like CD players, DACs etc. Also there is support in Windows media player for HDCD. Thus many people are able to use HDCD enhanced records, but there is a lack of HDCD encoded material. Having ffmpeg being able to encode HDCD HDCD-enabled equipment could be used more effectively.

I haven't found any software to do the job and the hardware equipment to encode HDCD is very expensive or not even available.

Thanks for considering.

(1) ​http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=1&f=G&l=50&co1=AND&d=PTXT&s1=5479168.PN.&OS=PN/5479168&RS=PN/5479168