HDCD CDs and transcoding

[AdamWysokinski]

Hi,

Any idea if transcoding with flac:wav24 would have the same effect for HDCD tracks ripped to standard 16/44 flacs as converting these files with a dedicated plugin (hdcd.exe or sth. that is implemented in the dBpoweramp)?
hdcd.exe produces 20-bit wav files, while dBpoweramp gives 24-bits files.

Regards,
Adam

[simoncn]

(17-05-2014 11:04)AdamWysokinski Wrote:  Hi,

Any idea if transcoding with flac:wav24 would have the same effect for HDCD tracks ripped to standard 16/44 flacs as converting these files with a dedicated plugin (hdcd.exe or sth. that is implemented in the dBpoweramp)?
hdcd.exe produces 20-bit wav files, while dBpoweramp gives 24-bits files.

Regards,
Adam

If you rip an HDCD track to a 16/44.1 FLAC file, the HD information (extra 4 bits) is lost permanently and can't be restored by later transcoding. Ripping these files to 20-bit WAV or 24-bit FLAC preserves the extra 4 bits. By ripping to 24-bit FLAC and transcoding this to WAV for playing, you should get the best of both worlds.

Edit: The above information is incorrect. The HDCD information is still present in a 16/44.1 FLAC file, but in a special format that isn't detected when doing flac:wav24 transcoding. The only way to retrieve this information using MinimServer is to rip the HDCD to a 24/44.1 FLAC file.

[AdamWysokinski]

Thanks Simon.

[Soli]

(17-05-2014 16:27)AdamWysokinski Wrote:  Thanks Simon.

That is actually wrong. HDCD properties are buried in LSB. Would be nice to have minimserver scan all the files and put HDCDs under an own HDCD folder.

[simoncn]

(02-06-2014 23:18)Soli Wrote:  That is actually wrong. HDCD properties are buried in LSB.

Thanks for the clarification. I've updated my earlier reply. I haven't been able to find any information about the LSB encoding format and how it is detected by hdcd.exe and similar programs. Can you provide a pointer to this information?

Quote:Would be nice to have minimserver scan all the files and put HDCDs under an own HDCD folder.

From reading other posts on this subject, I have the impression that doing this scanning for all 16/44.1 files would be very costly and would therefore add significantly to the time taken to rescan the library.

[Soli]

Its probably patented etc.
At least according to Wikipedia: In 2007, a member of the Doom9 forum authored a Windows CLI utility, hdcd.exe, to extract and decode the HDCD data in 16-bit WAV files ripped from HDCD discs. This utility writes 24-bit WAV output files with four bits of padding per sample. The author of the utility decided not to make the source code publicly available as the HDCD technology is patented.[10]

HDCD are 2 things: a good ADC with dither/noiseshaping, and the specific HDCD features, where Peak Extend is more or less the only one that matters.
In isolation HDCD is a quite simple "DBX" type process that use the signals coded/buried within LSB to tell the HDCD decoder how much the signal should be expanded. HDCD with peak extension have the possibility to sound better than normal CDs, it can sound close to a real 19-20bit properly mastered file. Not because HDCD has any real 20 bit resolution, the max resolution is still 16bit, but using peak extend and dither/noiseshaping you can have 16it sound down to approx -20-24db (the number MAY be inaccurate but the point would be the same). And the dynamic range can almost be the same as 20bit, but with 16bit resolution. These features, along with the Pacific Microsonic ADC which is among the worlds best ADCs, along with proper mastering (since HDCD is actually an ADC process, you are mostly spared the ultra evil digital loudness war mastering), will result in a really good sounding music But the good sounding music is not the result of HDCD itself, if you turn off peak extend, it will still sound good, and it will sound better on DAC that don't support HDCD.

Heres a picture that illustrates the waveform when peak extend is properly decoded:
http://i60.photobucket.com/albums/h39/mo.../gdwav.jpg

Since peak extend makes the recording sounding worse, most studios that use the HDCD processors for their sound quality , actually turn peak extend off.

[simoncn]

(03-06-2014 08:57)Soli Wrote:  Its probably patented etc.
At least according to Wikipedia: In 2007, a member of the Doom9 forum authored a Windows CLI utility, hdcd.exe, to extract and decode the HDCD data in 16-bit WAV files ripped from HDCD discs. This utility writes 24-bit WAV output files with four bits of padding per sample. The author of the utility decided not to make the source code publicly available as the HDCD technology is patented.[10]

HDCD are 2 things: a good ADC with dither/noiseshaping, and the specific HDCD features, where Peak Extend is more or less the only one that matters.
In isolation HDCD is a quite simple "DBX" type process that use the signals coded/buried within LSB to tell the HDCD decoder how much the signal should be expanded. HDCD with peak extension have the possibility to sound better than normal CDs, it can sound close to a real 19-20bit properly mastered file. Not because HDCD has any real 20 bit resolution, the max resolution is still 16bit, but using peak extend and dither/noiseshaping you can have 16it sound down to approx -20-24db (the number MAY be inaccurate but the point would be the same). And the dynamic range can almost be the same as 20bit, but with 16bit resolution. These features, along with the Pacific Microsonic ADC which is among the worlds best ADCs, along with proper mastering (since HDCD is actually an ADC process, you are mostly spared the ultra evil digital loudness war mastering), will result in a really good sounding music But the good sounding music is not the result of HDCD itself, if you turn off peak extend, it will still sound good, and it will sound better on DAC that don't support HDCD.

Heres a picture that illustrates the waveform when peak extend is properly decoded:
http://i60.photobucket.com/albums/h39/mo.../gdwav.jpg

Since peak extend makes the recording sounding worse, most studios that use the HDCD processors for their sound quality , actually turn peak extend off.

This information is interesting but it doesn't explain how to identify or decode the additional HDCD data that is present in a 16/44.1 FLAC rip of an HDCD disc. Perhaps the specification that describes this isn't available in the public domain.

[Soli]

I suspect the other tools have come from reverse engineering and are not open source. Microsoft owns HDCD now, although they seem to have trashed it.
HDCDkinda useless nowadays anyways, as a couple of todays top ADCs sound just as good/better, and then you dither the resulting 24bit file down to 16bit with various dither-algorithms and get music that sound in all DAC not just HDCD capable DACs. Of course the same goes with HDCD files that arent coded with HDCD specific features. It's just that you never can be sure until you have analyzed them, so it's a minor pain in the ass. Just like de-emphasis was.

[GreenMtnGringo]

Hi Simon. I would be very interested in HDCD decoding in MinimServer, as well. Historically, I have ripped HDCD discs to 24-bit, 44.1k FLAC using dBpoweramp. But I have read that these rips are not necessarily 'lossless.' As I understand it, the best practice would be to rip HDCD discs as standard 16-bit, 44.1k FLAC files and then have the HDCD information embedded in those FLAC files decoded by the media player. I play FLAC files using MimimServer, so I have often wondered if there is a way for MinimServer to do the HDCD decoding of a 16-bit, 44.1k FLAC rip of an HDCD disc.

The Foobar2000 media player handles HDCD decoding using the optional/free HDCD.exe plug-in. See:

https://www.foobar2000.org/components/view/foo_hdcd

Is there some way to incorporate this plug-in into MinimServer?

Thanks very much.

[simoncn]

You are correct that HDCD tracks are best ripped as standard 16-bit, 44.1k files containing the encoded HDCD audio. To use MinimServer to decode these files correctly for optimal sound quality, you should do the following:

1) Install MinimStreamer 0.7.13 and FFmpeg on the machine running MinimServer.

2) Use the stream.transcode property to transcode your HDCD files to wav24. If these files are encoded as FLAC, the transcoding setting must be followed by a semicolon (flac:wav24; instead of flac:wav24) to ensure that FFmpeg is used for transcoding.

3) In the stream.options property, add the option convOut=-af hdcd to enable the FFmpeg hdcd filter. This filter recognises HDCD-encoded audio and decodes it correctly for playback.

I have tried this on a sample HDCD file and the improvement is very noticeable.