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Discussion Starter · #1 ·
I know that there is no way to have current models of RPTV record a "DIGITAL DOLBY 5.1" audio track.


But my A/V receiver is telling me that on playback that there is a "SURROUND" track being played.


Now as one of the automatic features of my A/V receiver is to convert a one/two channel audio track into a multi-audio playback [phase shifting, time delaying, sending sub-sonics to the sub-woofer]... and when it does this the display shows "SURROUND" just as if I was playing a VHS tape that has confirmed "DOLBY SURROUND".


I can not seem to turn off this feature of the A/V reciever.


So in short my question is...


Does the RPTV really save the "DOLBY SURROUND" sub-track?


--David
 

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I believe the audio coming out of the digital out is PCM. At least, that is what my receiver tells me whenever I switch over to the Replay Input.
 

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Discussion Starter · #3 ·
I thought that PCM was a recording/storage format, which as far as I can find so far in going 'Google's could/maybe store "DOLBY SURROUND" info..


The question is.. does they way that RPTV store the audio info preserve the "DOLBY SURROUND" info? OR does the info get lost in the encoding process?


--David
 

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Dolby pro-logic is a matrixed encoding format. 4 channels of audio are encoded into a 2 channel mix. If a program is being broadcast in this format it will be preserved by whatever is recording it.
 

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I have the same issue that just started a few days ago. My Kenwood VR-6070 now starts to play the program recorded or live in 5.1 digital. The receiver is set to "auto" and always finds the correct signal to play. It has never done this before while using RPTV. It usually plays in stereo mode only. I have always used the optical connection between the Replay and receiver. Did Replay change something in the software?
 

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I have a kenwood vr-4700, haven't had any problems lately. The receiver detects it as a pcm digital signal, I'm running it on full auto, and then select dolby surround... works great!
 

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Discussion Starter · #7 ·
So from the replies [and 'Googling] I can take it that the RPTV is storing the "DOLBY SURROUND" info..


Next question.. when moved to a PC Via "DVA" and then re-encoded to a DVD does the encoded DVD then have the "DOLBY SURROUND" info??

:confused:



I know to date that there is not a true "DOLBY DIGITAL" DVD encoding software for consumer level DVD authoring software.


Just day dreaming here but it would be nice "IF" there was a way to take the ""DOLBY SURROUND" info and convert it to "DOLBY DIGITAL" at the consumer level.


--David
 

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There's lots of confusion with the regards to the different audio formats...


Dolby Digital, comes in many flavors, but it's a digital transport stream. And being a digital stream there's no way for it to get into the replayTV. Every format from 2/0 to 7.1 you can't record it.


Dolby Prologic - a matrixed encoded 2 channel audio stream that can be decoded into 4 channels. The 4 channels are left, center, right and surround.


The replay records whatever comes in. If the source is dolby prologic the output will be prologic.


The replay records the stereo audio as a 48k mpeg-I Layer II audio stream.


When the replay outputs the audio it decodes it to a 48k PCM stereo signal. This stereo signal can be output through the toslink connector as 48K PCM audio.


What the recieve does with the PCM data depends on the reciever. If your reciever can decode ProLogic audio it will decode to 4 channels. The only other option is 2 channel stereo audio.


Each of my recievers says something different, the output is the same, but the description on the display is different.


The only thing the replay can record is 2 channel audio, an
 

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David, if your source is stereo, like the replay records the most you can expect to get is a DD 2/0 encoding. And I do that for my DVDs. You can use a DD encoder from Sonic or SonicFoundry's Sound Forge. You can also look into the freeware BeSweet for a free transcoder. BeSweet is complicated you don't understand audio,and it sounds like you don't yet. Look at BeSweetGUI to help you out.


Ask away if you have transcoding questions. =)
 

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Discussion Starter · #10 ·
Quote:
Originally posted by Jeff D
There's lots of confusion with the regards to the different audio formats...

>
 

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Quote:
Originally posted by DavidEC
The main question comes about because the RPTV devices seem to have trouble recording "Closed Captions" which is part of the video transmission signal... so just wanted to make sure that the audio signal was not getting "REMIXED" (For lack of a better way to post my thought) when being recorded to the harddrive to save space.


--David
Now I think I understand better....


You are asking if the audio encoding to MPEG-1 Layer 2 format loses the Prologic encoding?
 

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Discussion Starter · #12 ·
Quote:
Originally posted by Jeff D
Now I think I understand better....


You are asking if the audio encoding to MPEG-1 Layer 2 format loses the Prologic encoding?
Thats the question!! Just did not know how to phrase it..


So whats the answer?


--David
 

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DavidEC, the correct term for this kind of "Surround Sound" is Dolby Pro-Logic.


Yes the Replay will record Pro-Logic if the source itself outputs Pro-Logic. Some TV Shows do, some don't. I know 24 does on Fox, but most other Fox shows do not.


Will this be preserved if you take your Replay TV MPG and burn it to DVD? Yes.
 

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Quote:
Originally posted by Jeff D
David, if your source is stereo, like the replay records the most you can expect to get is a DD 2/0 encoding. And I do that for my DVDs. You can use a DD encoder from Sonic or SonicFoundry's Sound Forge. You can also look into the freeware BeSweet for a free transcoder. BeSweet is complicated you don't understand audio,and it sounds like you don't yet. Look at BeSweetGUI to help you out.


Ask away if you have transcoding questions. =)
I've started using Nero Vision Express 2 to author my replay DVDs because it allows you to select DD 2.0 as an audio option. If I burn a disc with Mpeg audio I'm forced to go into the audio setup of my dvd player and select PCM audio output or I get no sound. Changing the audio to DD avoids this problem.
 

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bkoester, that's why I do it too.. I want the ease of use when I can just play DD audio without any problems. It's extra work on the front end, but easier in the long run.
 

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Quote:
Originally posted by djdementia
DavidEC, the correct term for this kind of "Surround Sound" is Dolby Pro-Logic.


Yes the Replay will record Pro-Logic if the source itself outputs Pro-Logic. Some TV Shows do, some don't. I know 24 does on Fox, but most other Fox shows do not.


Will this be preserved if you take your Replay TV MPG and burn it to DVD? Yes.
Forgive me for a bit of pedantry here, but: "Dolby Pro-Logic" (as well as "Dolby Pro Logic II" and even "Dolby Surround" are *decoding* schemes that derive results from stereo sources with phase-encoded surround information (there is no formal name for this process that I am aware of beyond "surround sound", though Dolby has licenced its name to various shows and networks).


So another way of stating the question is "does Replay/MPEG2-encoded stereo audio retain phase information sufficient to demodulate surround sound?" The answer to this appears to be "pretty much", though the results are highly dependent on bitrates and (as you say) the quality of the incoming signal.


As to the question about burning to DVDs, again the answer is a bit more complex. DVD audio can be in the form of PCM stereo, or one of several flavors of Dolby Digital (unrelated to the Dolby analog decoding methods mentioned above), or, I suppose, DTS (though I don't think this last is supported by home burner software). PCM stereo at reasonable bitrates does maintain phase relationships; the decoded analog result of such a signal can be processed by an *analog* decoder (the same Dolby Pro Logic or other surround decoder used to decode the original broadcast, for exampe) and any surround information will still be there. Dolby Digital audio tracks from such sources, on the other hand, may be produced in one of two ways: a stereo (DD 2.0) track, which again must be decoded from the analog output into multi-channel sound using phase information, or multi-channel (DD 3.0/3.1, 4.0/4.1, 5.0/5.1) tracks. In this latter case the DVD authoring program must pre-process the original stereo audio and derive the equivalent surround information, then create *dedicated* audio tracks for each channel. This type of format can now be decoded digitally by a Dolby Digital processor directly to each channel.


JGM
 

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Nice post JGM, I started to type all that out, then decided it was overkill for the topic at hand.


The only thing I'd add, is for DTS it's do-able, but you'll need a DTS encoder of which there is only one commercial one and it cost like $10k. There's no need to do that!
 
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