[albain]

LAST EDIT : 01/02/2010

Hi,

we now have on FFDShow Tryout a fully functional HD audio bitstream to the HDMI output of your sound/graphic adapter.

What is bitstream :
first there are compressed formats (MP3, MP2, AC3,DTS) and uncompressed formats (PCM, LPCM).

Among those compressed formats there are the new high definition audio formats : Dolby True HD, DTS-HD HR (High Res), DTS-HD MA (Master Audio, the best format)
There is also Dolby Digital Plus which is an improvement of Dolby Digital but less good than Dolby TrueHD
Lastly, Dolby TrueHD and DTS-HD MA are considered as lossless quality, which means that once uncompressed the quality is even as if they were not compressed at all

Compressed formats need to be decoded before sending them to your receiver or speakers.

However, it is possible to let the stream go compressed and send it to your receiver so that it takes in charge the decoding.
This was the case for AC3 and DTS : it is called SPDIF (going through a numeric opticial or coaxial output)

Now, new HD audio formats such as Dolby True HD, Dolby Digital Plus and DTS-HD (High Resolution or Master Audio) can also be sent compressed to the receiver.
This is called bitstream.
A HDMI output is required to do that (SPDIF has not a sufficient bandwidth).

This is interesting as receivers can be considered as better decoders than software decoders and furthermore there is no existing free DTS HD software decoder yet.

What has been done on FFDShow Tryout :
- bitstream support for TrueHD, DTS-HD (HR & MA) using the new radeon 5xxx series on Vista and Windows 7 (32 & 64 bits). Depending on the OS and the format, some audio renderers may not work. Try several : directsound, waveout and MPC renderer
- TrueHD, DTS HD and Dolby Digital Plus bistream are working on the xonar (Vista and Windows 7). waveout and Arcsoft renderer work well.

What needs to be fixed or improved :
- Dolby Digital Plus bitstream on ATI 5xxx : this is likely due to a driver issue (ATI drivers don't support DD+ yet)
- auzentech : no HD bitstream support because the streams are encrypted by the software (powerdvd) to the audio driver. Ask Auzentech to bring support for third party players
- LPCM support to be added (on 24 bits sampling at 48000/96000/192000 Hz, LPCM 16 bits is already supported)

The HD audio bitstream is now integrated to FFDShow Tryout daily builds and the bugs have been fixed since revision 3241

Supported (and tested) hardware This list may grow up in the future
- ATI Radeon 5xxx series
- Asus Xonar
- Intel clarksdale


Setup :
- Install FFDShow Tryout revision 3241 or greater, 32 or 64 bits
- On Vista : you will need the MPC audio renderer. It is very recent and in early stage but it is functional.
- On windows 7 : default directsound renderer should work on most bistream formats. Otherwise use the waveout renderer or MPC renderer
- If you have a xonar : won't work with directsound renderer, the best is to use the the arcsoft renderer (on a dos window in administrator mode : regsvr32 (total media path)\codecs\asrenderer.dll). Otherwise try the waveout or MPC renderer (don't know if they will work)
- Player software :
1/MPC-HC : you will have to grab a very recent version of MPC-HC (revision 1413 or greater). If you don't have the right version the MPC mpeg splitter will break the DTS HD streams and the MPC renderer won't work
2/Other directshow players (WMP,...) : you will need MPC-HC *recent* standalone filters (revision 1413 or greater). Just register MPC audio renderer and MPC mpeg splitter. For MKV Haali media splitter should work too


Status for ATI 5xxx series owners
There are 2 know issues with ATI 5xxx :
- Audio dropouts that occur every few seconds : this issue is not caused by FFDShow and it occur on any software player without hardware acceleration (no DXVA, or called software decoding). Please post a ticket to AMD support for this
- The receiver that aren't caught up by the radeon : also a driver bug, there is a workaround for this, called "tulli's override", the person who found this hack (see below)

(with-if needed- or without tulli's override monitor driver)

- Windows Seven:
Just with Ati 9.12 hotfix drivers:
DTSHD: no problem with PDVD9 and MPC-HC (ffdshow 54+ MPC Audio Renderer)
THD: No problem with PDVD9 and the best renderer is Ati HDMI Output for MPC-HC (with ffdshow 54)

Realtek 239 over 12 hotfix:
Both HD formats may use Default DirectSound Device.

- Windows Vista:
ffdshow HD bitstreaming only works with Ati 9.12 hotfix drivers by alone using MPC HC Audio renderer on Vista; Realtek 239 doesn't work.
While PDVD9 can work even Realtek 239 is loaded over 9.12 hotfix.