Handling of DTS audio in ReClock

[p0ddie]

Hi there,

first of all I wanted to take the time to say a big THANK YOU for continuing to develop ReClock - I would be lost without it!

Having used the "original" last version for a couple of months now, I got tired of the sound hickups when watching PAL media on a 24p screen and installed ReClock 1.8.3. First things first: The re-encoding of audio worked out of the box, actually without even changing settings.


Here is question 1: Sadly, my AMD 5200+ EE seems to be a little to weak to re-encode audio at the highest setting ("Excellent") and still having enough headroom to play a 1080p mkv file (while doing some smaller stuff in the background).

Is it possible to tell ReClock to re-encode audio only with selected media, such as PAL dvds? The old ReClock version worked fine for me, adapting 23.9xx Hz to 24 Hz without re-encoding, and it saves a lot of cpu cycles. So what I would love is the ability to use spdif passthrough whenever I watch a 24Hz file and re-encoding after resampling only if I use 25Hz media.

Question 2: What happens to DTS soundtracks? I just tried out, there still seems to be 6 channel surround sound, but my receiver says "Dolby Digital" with a DTS soundtrack. So, I figure the DTS audio gets re-encoded to DD, that's why the receiver shows. Is there some way to circumvent this and have either a DTS re-encoding or, as qith question 1, just passthrough?

I figure if I have a DTS soundtrack re-encoded to DD, there should be some loss in dynamics and quality, right?


Thanks for your help and sory for not being brief, but I thought I'd rather point out exactly what my "problems" are. If you guys are German, let me just point out that my problem is "jammern auf hohem niveau" (whining at the highest stage)...

 

[Jong]

Not what you were looking for, but try the new resampler: http://forum.slysoft.com/showthread.php?p=156475#post156475

This uses about half the CPU in v.good/excellent mode as earlier builds. Also the build you get this way balances itself across multiple cores; The version that comes with Reclock hits one core very hard. You may find this allows you to resample without compromise.

 

[p0ddie]

hey,

thanks, I'll give it a try later on

Just a thought: wouldn't it make sense to re-encode to DTS all the way, even with AC3 output? Is there a library that does that? sorry for my complete lack of knowledge in this area, but this way there would be no quality loss for DTS audio tracks.

 

[James]

hey,

thanks, I'll give it a try later on

Just a thought: wouldn't it make sense to re-encode to DTS all the way, even with AC3 output? Is there a library that does that? sorry for my complete lack of knowledge in this area, but this way there would be no quality loss for DTS audio tracks.

I don't know of a DTS library, and there would be the same quality loss. AC3 is fine.

 

[deandob]

What about no resampling with HD sources

I have a similar question, is it possible to use reclock for HD sources (blu-ray and HD DVD) without resampling the audio? I have a high end audio system and am very wary of resampling audio especially with the new lossless codecs which sound great.

If it is not possible, can someone comment on the audio quality loss when resampling?

thanks.

 

[CraziFuzzy]

If you disable the AC3 encoder in ReClock, and enable 'Accept SPDIF sources', I believe it passes the digital audio through, untouched. Though you would lose any timestretching/resampling you might be doing.

 

[James]

If you disable the AC3 encoder in ReClock, and enable 'Accept SPDIF sources', I believe it passes the digital audio through, untouched. Though you would lose any timestretching/resampling you might be doing.

... which pretty much defeats ReClock's purpose - to sync the audio and video clocks.

 

[CraziFuzzy]

... which pretty much defeats ReClock's purpose - to sync the audio and video clocks.

Depends on your situation. Audio and Video are synced together just fine without ReClock. I use ReClock for syncing playback speed to the video clock, and in my case, for setting the refresh rate to the media playback speed.

 

[deandob]

CraziFuzzy,

Can you explain what you are doing? Doesn't reclock lock on the audio clock not the video clock?

James,

What about if you want to use reclock to smooth video motion, and not concerned with the audio speed adjustment? Or does the audio move out of sync over time and lipsync becomes an issue?

Also, how do you resample the DTS-MA / TrueHD? Do you re-encode them to the lossy AC3/DTS core at lower bitrates? IMO resampling the lossless codecs to a lower bitrate lossy core sacrifices some of the advantage of Hi-Def media.

If you don't want to resample and the sync is an issue (ie. reclock is not a fit) - is the only other solution to purchase a high quality video card with a better clock?

Sorry for the noob questions, but I have read the reclock instructions as well as this forum and I can't work out the answer. I would have thought that many HTPC Hi-Def fans would want to use reclock without audio resampling.

 

[James]

Also, how do you resample the DTS-MA / TrueHD? Do you re-encode them to the lossy AC3/DTS core at lower bitrates? IMO resampling the lossless codecs to a lower bitrate lossy core sacrifices some of the advantage of Hi-Def media.

Use LPCM over HDMI. Problem solved.

 

[James]

Depends on your situation. Audio and Video are synced together just fine without ReClock

Sure. This is *not* the point.

 

[CraziFuzzy]

CraziFuzzy,

Can you explain what you are doing? Doesn't reclock lock on the audio clock not the video clock?

No, you are describing normal directshow behavior. Normally, the clock that is used for metering playback is the clock from the Audio drivers (via the Audio Renderer filter). This causes less than smooth playback, as the display playback rate is not necessarily related to the refresh rate in any way. This is what ReClock was originally designed to correct. It loads as an audio renderer, so that directshow doesn't know any better, and it locks the playback to the refresh rate, instead of the audio clock, preventing the herky jerky playback. The fact that it was an Audio renderer, and the audio was passing through it anyways, allowed the timestretching features to be added, to adjust for pitch problem related to larger time adjustments (such as PAL vs. FILM adjustments).

For me, the killer feature of ReClock is the vbs notifications, allowing me to adjust resync my display to the optimal display rate for each video i play. This has really improved the playback of ALL content.

 

[deandob]

Thanks CraziFuzzy, James,

I think I have it now, match the video card refresh rate to the source refresh rate. I did use an earlier version of reclock for PAL speedup a couple of years back, but now as I watch mostly HiDef in my theater the 2 things I'm looking for now from reclock is smoother playback and no loss of audio quality.

James, is it still possible to use reclock without audio resampling for analog output? I have a pro-audio soundcard and don't use a receiver. Can you also confirm that there are no audio dropouts or lipsync problems if the audio is not resampled?

Also, Happy New Year!

 

[James]

James, is it still possible to use reclock without audio resampling for analog output?

Why by all means would you do that? Or do you mean AC3 encoding?

I have a pro-audio soundcard and don't use a receiver. Can you also confirm that there are no audio dropouts or lipsync problems if the audio is not resampled?

ReClock resamples because then there won't be audio dropouts.

EDIT: Read the manual. Analog output will be fine.

 

[deandob]

Thanks James.

I think I've got it, in summary, for Blu-Ray and HD DVD with analog output you have to resample the audio (which re-encodes using a resampler and a lossy codec like AC3) else you get audio dropouts due to the frame rate adjustment between the audio & video.

 

[James]

Thanks James.

I think I've got it, in summary, for Blu-Ray and HD DVD with analog output you have to resample the audio (which re-encodes using a resampler and a lossy codec like AC3) else you get audio dropouts due to the frame rate adjustment between the audio & video.

Erm... when using analog outputs there won't be any "lossy re-encode".
Re-encoding will only be done if using SPDIF connections.

 

[deandob]

Duh - of course! Thanks James.

The only adjustment then is the resampling, so the analog output is actually capable of keeping the audio quality high. I use the Rabbit resampler for redbook audio and it sounds good on my system, so it should be fine in reclock. I'll give it a test drive.

 

[Barleyman]

Some follow-up questions WRT handling dts..

Can I set the recoding bitrate? It's a bit funky to encode BD 1.5Mbps DTS track to 448kbit/s AC3 track..

640kbit/s probably wouldn't make too much double-blind-testable difference, but it'd make ME feel better!

I just recently invested in BD upgrade for my HTPC and got hit by serious judders in BD playback. PAL speedup should help and a bit of research led me here!

Ed: Apparently the only realistic ooption for DTS recoding would be Xonar, that'd set me back another 90 euros..

 

[James]

Some follow-up questions WRT handling dts..

Can I set the recoding bitrate? It's a bit funky to encode BD 1.5Mbps DTS track to 448kbit/s AC3 track..

640kbit/s probably wouldn't make too much double-blind-testable difference, but it'd make ME feel better!

Well, you may feel better now. ReClock's AC3 encoder always encodes to 640kBit/s, not 448kBit/s.