[pulseaudio-discuss] [WIP] Passthrough support

[Dark Shadow]

On Thu, Mar 24, 2011 at 7:19 PM, Kelly Anderson
<kelly at silka.with-linux.com> wrote:
> On 03/24/11 18:58, Dark Shadow wrote:
>>
>> On Thu, Mar 24, 2011 at 10:50 AM, Anssi Hannula<anssi.hannula at iki.fi>
>>  wrote:
>>>
>>> On 24.03.2011 16:18, pl bossart wrote:
>>>>>
>>>>> It seems that 384k sample rates aren't supported directly in alsa, I
>>>>> did
>>>>> some patching to no avail yet.
>>>>>
>>>>> In any case if the channel count can be specified with passthrough the
>>>>> following should work.
>>>>>
>>>>> paplay --raw --channels=2 --rate=192000 --passthrough
>>>>> File.dts.spdif192khz (
>>>>> this works).
>>>>>
>>>>> paplay --raw --channels=4 --rate=192000 --passthrough
>>>>> File.dts.spdif384khz (
>>>>> this fails).
>>>>>
>>>>> To passthrough dolby true-hd it looks like it'll be necessary for more
>>>>> than
>>>>> two channels to work.
>>>>
>>>> There was a thread on dts-hd in alsa-devel at some point. Anssi
>>>> (cc:ed) contributed some patches for HDMI and provided the information
>>>> below on ffmpeg configurations.
>>>> You may want to try at the alsa level before trying with pulseaudio to
>>>> make sure your setup is correct. I tend to believe you have to go for
>>>> 8ch @ 192kHz to make this work based on my limited understanding of
>>>> HBR.
>>>
>>> Indeed for HBR you need to always specify 8 channels and use rate to
>>> control the final rate (i.e. you either use "normal" 2 channel
>>> passthrough or HBR 8 channel passthrough).
>>>
>>> For example to passthrough the abovementioned 384 kHz stream you need to
>>> use 8 channels and rate of 96000. However, I think 384kHz DTS bitstream
>>> is generally *not* supported by A/V receivers, so you probably want to
>>> use 768kHz (8 channels, 192kHz).
>>>
>>> (note: I haven't tested whether HBR works with pulseaudio or not)
>>>
>>>
>>>> The DTS-HD part is not merged yet (patch is in ffmpeg-devel@), but the
>>>> TrueHD and E-AC-3 support is already there in ffmpeg trunk.
>>>>
>>>> The ffmpeg commandline to use is:
>>>> ffmpeg -i input.file -f spdif output.spdif
>>>>
>>>> For DTS-HD files, to get full passthrough (i.e. not only core), a
>>>> -dtshd_rate parameter is needed, which sets the output IEC958 rate.
>>>> ffmpeg -i input.file -f spdif -dtshd_rate 192000 output.spdif
>>>> ffmpeg -i input.file -f spdif -dtshd_rate 768000 output.spdif
>>>> 192000Hz is enough for streams that have a bitrate below 6.144Mbps,
>>>> which
>>>> means all DTS-HD High Resolution Audio files and even many of the DTS-HD
>>>> Master Audio (the latter are lossless VBR).
>>>>
>>>> To play the spdif files back, I use
>>>> aplay -D hdmi:CARD=$CARDNAME,DEV=$DEVICENUM,AES0=0x06 -c $CHANCOUNT -r
>>>> $RATE file.spdif
>>>>
>>>> - replacing $CARDNAME with the card name
>>>> - replacing $DEVICENUM with 0..3 depending on card and hdmi port (for
>>>> non-zero DEVICENUM you'll need a patch from alsa git:
>>>>
>>>> http://git.alsa-project.org/?p=alsa-lib.git;a=commitdiff;h=e6d5dcf1f625984605d362338d71162de45a6c60
>>>> )
>>>> - set $CHANCOUNT and $RATE as per below
>>>>  - rate 192000 and channels 2 for IEC958 rate 192 kHz (for e.g. 48 kHz
>>>> E-AC-3, and DTS-HD when the IEC958 rate was set to 192000 in ffmpeg)
>>>>  - rate 192000 and channels 8 for IEC958 rate 768 kHz (for most TrueHD
>>>> files, and for DTS-HD when the rate was set to 768000)
>>>> - note that having the 0x02 bit (non-pcm) set in AES0 is mandatory when
>>>> $CHANCOUNT is larger than 2, as ALSA uses it to determine whether to use
>>>> HBR or not. The additional 0x04 (non-copyright) I use above is not
>>>> mandatory, but is the alsa default so I kept it.
>>>
>>> --
>>> Anssi Hannula
>>> _______________________________________________
>>> pulseaudio-discuss mailing list
>>> pulseaudio-discuss at mail.0pointer.de
>>> https://tango.0pointer.de/mailman/listinfo/pulseaudio-discuss
>>>
>> Would anyone know where I could get a hold of some DTS-HD samples in
>> 192Khz and 384kHz for testing?
>
> You can extract the dts-hd tracks from your mkv's with mkvextract.  You can
> make them with spdifer (part of AudioFilter).
>
>
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Unless I am missing something all the movies I play say 48kHz on my
receivers OSD when played through my PS3 so I thought that was the
best they have, and higher was not used on average Blu-Ray's.

If they have better why is it not being used considering my receiver
supports it. I know from this dmesg output

[  182.696452] HDMI: detected monitor TX-SR608
[  182.696456]     at connection type HDMI
[  182.696462] HDMI: available speakers: FL/FR LFE FC RL/RR RLC/RRC
[  182.696472] HDMI: supports coding type LPCM: channels = 2, rates =
44100 48000 88200 176400 192000 384000, bits = 16 20 24
[  182.696481] HDMI: supports coding type LPCM: channels = 8, rates =
44100 48000 88200 176400 192000 384000, bits = 16 20 24
[  182.696489] HDMI: supports coding type AC-3: channels = 8, rates =
44100 48000 88200, max bitrate = 640000
[  182.696495] HDMI: supports coding type DTS: channels = 8, rates =
48000 88200, max bitrate = 1536000
[  182.696501] HDMI: supports coding type DSD (One Bit Audio):
channels = 6, rates = 48000
[  182.696507] HDMI: supports coding type E-AC-3/DD+ (Dolby Digital
Plus): channels = 8, rates = 48000 88200
[  182.696514] HDMI: supports coding type DTS-HD: channels = 8, rates
= 48000 88200 176400 192000 384000
[  182.696520] HDMI: supports coding type MLP (Dolby TrueHD): channels
= 8, rates = 88200 192000