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How do I know if a track is LtRt or LoRo without an A/V receiver?

4 Replies, 817 Views

I have some 2.0 tracks (Dolby Digital and lossless) that I would like to synchronize but I have several doubts.

1) Is Dolby Digital 2.0 Surround what is also called LtRt and Dolby Digital 2.0 Stereo is LoRo or are they different things?

2) If the above answer is affirmative, how do I know if a track is LtRt or LoRo without an AV receiver? As far as I know, with a 2.0 Surround track an AV Receiver using Dolby Pro-Logic (not Dolby Pro-Logic II, Dolby Pro-Logic IIx, Dolby Pro-Logic IIz…) will provide me with 4 channels: Left, Center, Right and Mono Surround. But what happens with a 2.0 Stereo track if I select Dolby Pro-Logic? I’ve read in some forums that with Dolby Pro-Logic the track will play as LCRS with 2.0 Surround but only as LR with 2.0 Stereo and as C if 2.0 Mono. But I think in the case of 2.0 Stereo they are wrong, I don't know.

3) Even without an A/V Receiver I think it’s possible to find out if a 2.0 track is Surround or Stereo, If I am not mistaken, Dolby Digital tracks can have a Dolby Surround flag added to them. This way, Pro-Logic decoding will occur automatically during playback. But I believe that LPCM/FLAC/WAV tracks cannot have that Dolby Surround flag. Therefore, I don't know how to find out if a 2.0 track is encoded as Surround. If it is, I want to keep the matrix encoding when exporting the tracks.
The matrix encoding is embedded into the audio stream, you won't lose anything exporting to another format. Your receiver will handle everything the same way and try and upmix whatever you give it, whether it be Dolby Surround or just stereo.

tbh just don't worry about it.
(2023-10-23, 10:21 PM)stwd4nder2 Wrote: The matrix encoding is embedded into the audio stream, you won't lose anything exporting to another format. Your receiver will handle everything the same way and try and upmix whatever you give it, whether it be Dolby Surround or just stereo.

tbh just don't worry about it.

Thank you very much stwd4nder2, but as I said, I don’t have an AV receiver. If the 2.0 track was previously converted from Surround to Stereo the mono surround channel will be affected. There must be some way to find out if the track is 2.0 Surround or has been converted to Stereo.

Does anyone have an answer for any of the questions?

1) Is Dolby Digital 2.0 Surround what is also called LtRt and Dolby Digital 2.0 Stereo is LoRo or are they different things?

2) With a 2.0 Surround track an AV Receiver using Dolby Pro-Logic (not Dolby Pro-Logic II, Dolby Pro-Logic IIx, Dolby Pro-Logic IIz…) will provide me with 4 channels: Left, Center, Right and Mono Surround. But what happens with a 2.0 Stereo track if I select Dolby Pro-Logic?

3) Dolby Digital tracks can have a Dolby Surround flag added to them. This way, Pro-Logic decoding will occur automatically during playback. But I believe that LPCM/FLAC/WAV tracks cannot have that Dolby Surround flag. Therefore, I don't know how to find out if a 2.0 track is encoded as Surround.
1) you should be able to tell if DD 2.0 is LtRt or not IF the proper flag is used AND its use is appropriate - I mean, you can encode a stereo track as DD 2.0 and flag it as surround, but it would not be magically converted to surround... :-)

2) you got sound from center speaker as if it was encoded as Dolby Surround - so basically it will sound "right"; as the surround channel was not intentionally encoded, it will be random, hence surround speaker(s) may sound "right" or "wrong".

3) is not possible to know for sure if a 2.0 track is encoded as (matrixed) surround - Dolby Surround, Circle Surround, Ultra Stereo etc.; you can only tell if it's mono (without having the chance to analyze waveforms) if playing that 2.0 track with Dolby Surround/Pro Logic I/II/IIx/IIz, Circle Surround, DTS Neo:6 decoder, you get sound only from the center channel.
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(2023-10-25, 08:34 PM)spoRv Wrote: 1) you should be able to tell if DD 2.0 is LtRt or not IF the proper flag is used AND its use is appropriate - I mean, you can encode a stereo track as DD 2.0 and flag it as surround, but it would not be magically converted to surround... :-)

2) you got sound from center speaker as if it was encoded as Dolby Surround - so basically it will sound "right"; as the surround channel was not intentionally encoded, it will be random, hence surround speaker(s) may sound "right" or "wrong".

3) is not possible to know for sure if a 2.0 track is encoded as (matrixed) surround - Dolby Surround, Circle Surround, Ultra Stereo etc.; you can only tell if it's mono (without having the chance to analyze waveforms) if playing that 2.0 track with Dolby Surround/Pro Logic I/II/IIx/IIz, Circle Surround, DTS Neo:6 decoder, you get sound only from the center channel.

Now everything is clear to me. Thank you very much.

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