HDCD CDs and transcoding

[vkshankar]

Setting or clearing the HDCD decode flag in the Oppo BDP 83 has no effect on the output level.
This means as Simon suspected, fb2k w/ HDCD decoder plugin is doing the best effort when constrained by 16 bit output. I guess that settles it.

[simoncn]

All this makes sense except for one thing. I would expect that the combination of sending an unmodified HDCD-encoded L16;44 stream and enabling HDCD decoding in the BDP-83 would result in correctly decoded HDCD audio from the player.

Is the input WAV file also 16/44 and an exact copy of the original CD audio data? If so, I wonder whether the BDP-83 does not apply HDCD decoding to data streamed across the network.

[simoncn]

I have found a combination that should (I think) make FFmpeg do a "best effort" conversion similar to foobar2000. Please try the stream.options setting

convOut=-af "hdcd,aresample=isf=s32"

[vkshankar]

(24-02-2021 09:52)simoncn Wrote:  All this makes sense except for one thing. I would expect that the combination of sending an unmodified HDCD-encoded L16;44 stream and enabling HDCD decoding in the BDP-83 would result in correctly decoded HDCD audio from the player.

Is the input WAV file also 16/44 and an exact copy of the original CD audio data? If so, I wonder whether the BDP-83 does not apply HDCD decoding to data streamed across the network.

It is my belief that HDCD encoding is not preserved in the wav:L16 conversion by fb2k. I will check this once more.

[vkshankar]

So I have decided to get rid of the Oppo BDP - 83 from my setup given its limitations. Instead I now have a TEAC NT-505. The TEAC NT-505 does not have HDCD decoder, so I am doing on the fly decoding with minimserver 2/minimstreamer with the following options:
stream.options -> convOut = -af hdcd -c:a pcm_s24le
stream.transcode -> wav:wav24
This works great if I play a HDCD encoded file. HDCD is decoded at the minimserver 2/minimstreamer end, and a 24bit stream is sent to the TEAC NT-505, thankfully this renderer can handle wav fmt. TEAC NT-505 gracefully plays and I definitely hear the 6db avg. attenuation vs. streaming the file with out the above mentioned option. Also ffmpeg logs show the per sample HDCD PE and LLE values indicating that HDCD decode is happening.
Now, if I play a regular wav file without HDCD encoding, I still have an avg 6db attenuation because of the stream.options and stream.transcode settings.
Is it possible to tell the minimstreamer to not kick-in and do the transcoding when regular file is played? Even if it means creating an .m3u file like what is done when handling network streams with the special formatting:

[id] name

In the below .m3u example, first 2 wav files would be transcoded, whereas 3 will not be handled by minimstreamer/transcoded

#EXTM3U
#EXTINF:229,[Minnesota] Dance of the Tumblers
01 Dance of the Tumblers.wav
#EXTINF:582,[Minnesota] Dance of the Seven Veils
02 Dance of the Seven Veils.wav
#EXTINF:252,Minnesota Hopak
03 Hopak.wav

Not sure about this, but just a thought.

[GreenMtnGringo]

(24-02-2021 16:16)vkshankar Wrote:  Is it possible to tell the minimstreamer to not kick-in and do the transcoding when regular file is played?

I raised this issue back in 2019 and it was determined that the answer is no, unfortunately. See post #17, above, and thereabouts. Maybe something has changed since then, I don't know. I gave up on Minimstreamer-based HDCD decoding after it became apparent that all playback is reduced by 6 dB regardless of whether the file is HDCD-encoded.

[simoncn]

You could add ReplayGain tags to the files you don't want to be reduced by 6 dB and use volume=replaygain=album or volume=replaygain=track in convOut.

FYI, you don't need -c:a pcm_s24le now that you have changed the transcoding output type to wav24.

[vkshankar]

(24-02-2021 18:45)simoncn Wrote:  You could add ReplayGain tags to the files you don't want to be reduced by 6 dB and use volume=replaygain=album or volume=replaygain=track in convOut.

FYI, you don't need -c:a pcm_s24le now that you have changed the transcoding output type to wav24.

Thanks. Will try this out.

[PhilE]

(24-02-2021 22:33)vkshankar Wrote:  

(24-02-2021 18:45)simoncn Wrote:  You could add ReplayGain tags to the files you don't want to be reduced by 6 dB and use volume=replaygain=album or volume=replaygain=track in convOut.

FYI, you don't need -c:a pcm_s24le now that you have changed the transcoding output type to wav24.

Thanks. Will try this out.

I have a handful of HDCDs that I'd like to try through the FFmpeg filter. From web searches all of them have the PE flag enabled. The rest of my libray consists of 16/44 FLAC files which all have Replaygain tags.

My current settings are:
stream.converter = ffmpeg
stream.transcode = flac:wav24;
stream.options = convOut=-af volume=replaygain=track

Can you please tell me if I'm correct in thinking that:

1. FFmpeg hdcd filter will decode the FLACs ripped at 16 bit because they are being transcoded to 24bit, and therefore I shouldn't/don't need to encode them with HDCD DSP (available in dBPoweramp)

2. I should change stream.options to:

convOut=-af "hdcd, volume=replaygain=track"

3. The FLAC files from HDCD rips shouldn't have Replaygain tags as this would mean the playback volume will be adjusted twice: reduced by 6dB by hdcd filter AND plus or minus the Replaygain tag value? If that were the case it may happen if I had ripped some HDCDs that didn't advertise they were HDCD (but it's very unlikely I have any)

If needed my renderer is Volumio running on Raspberry Pi. I don't think it is capable of HDCD playback.

Thanks

[simoncn]

I believe your assumptions are all correct. It isn't a problem if your HDCD files contain ReplayGain tags. Any such value should be combined with what the HDCD filter does, as you said in your post.