Dolby Surround from VHS to AC3

[Yakomo]

I have this Dolby Surround audio track from a VHS tape that I want to encode to AC3 for usage on DVD (it's a rare audio which is not available on dvd).

Of course I want to keep the Dolby Surround encoding, so my idea:
I attach a stereo VCR to the stereo inputs of a high quality DVD Recorder, which can record and encode the audio to 256kbps 48 khz DD2.0 AC3.

But: will the Dolby Surround information be preserved this way?

Thanks in advance!!

[SallyDog]

I attach a stereo VCR to the stereo inputs of a high quality DVD Recorder, which can record and encode the audio to 256kbps 48 khz DD2.0 AC3.

But: will the Dolby Surround information be preserved this way?

Thanks in advance!!

No. You are recording in stereo (2.0). DD2.0 is not surround.

[FlimsyFeet]

But: will the Dolby Surround information be preserved this way?!
Yes it will; the only disadvantage is that you cannot set the flag in the AC3 stream that indicates that Dolby Surround encoding is present.

[Yakomo]

Thanks for your replies! I thought so, but wasn't sure.

As it seems that it isn't possible to set the headers to "Dolby Surround encoded" to the ac3 I am considering letting the recorder encode into PCM instead and do the ac3 encoding myself.

I am using Sonic Audio Transcoder, what settings are correct to set the surround flag but not destroy the surround by applying another phase shift or any other unwanted effects for that matter.

This is what I would use, please tell me if I'm wrong:

Audio coding mode: 2/0 (?)

Dolby Surround mode: "Dolby Surround encoded"

Surround channel processing:
90-degree phase shift: off (?)
3 db attenuation: off (?)

Dialog normalization: -27dB (?)

[tebasuna51]

With Aften you can set the flag.

Edit: @Yakomo. Your settings are correct but i suggest you use Dialog normalization: -31dB to avoid the 4 dB attenuation from standard decoders.

[Yakomo]

Thanks for the fast reply, tebasuna51. What I ment was, it seems it is not possible to set the flag AFTER the ac3 has been encoded without it (like my recorder would have done).

Thanks for your hint, will set Dialog normalization to -31dB.

So, for turning an analogue source containing Dolby Surround encoding into a Dolby Surround AC3:

Encode settings:
Audio coding mode: 2/0
Audio bitrate: 256kbps

Bitstream information:
Bitstream mode: Complete main
Dolby Surround mode: Dolby Surround encoded
Dialog normalization: -31 dB
Sampling frequency: 48 kHz

Input filtering:
DC highpass filter: off
Bandwidth lowpass filter: off
LFE lowpass filter: off
Digital de-emphasis: off


Audio production information:
Include audio production information: off

Source material information:
Copyrighted material: off
Original bitstream: off

Compression
Dynamic Range Compression: none
RF overmodulation protection: off

Surround Channel processing:
90-degree phase shift: off
3 dB attenuation: off

Maybe this will help someone someday with a similar problem!

Thanks a ton for your help!

[tebasuna51]

What I ment was, it seems it is not possible to set the flag AFTER the ac3 has been encoded without it (like my recorder would have done).

It's possible. I make a litle util to do. I can send you if you need or wait to Justin (http://forum.doom9.org/showthread.php?t=143416) (Aften creator)

[specise_8472]

I have this Dolby Surround audio track from a VHS tape that I want to encode to AC3 for usage on DVD (it's a rare audio which is not available on dvd).

Of course I want to keep the Dolby Surround encoding, so my idea:
I attach a stereo VCR to the stereo inputs of a high quality DVD Recorder, which can record and encode the audio to 256kbps 48 khz DD2.0 AC3.

But: will the Dolby Surround information be preserved this way?

Thanks in advance!!

You could use the Surcode DPLII en / de coder to extract the stream into its discrete channels, then reencode AC3. Of course you could use Graphedit and any of the Nero, Sonic etc decoders to get the channels seperated.
If you can if you get the right decoder and AC3 encoder, do the whole process of extraction then encoding in Graphedit in one hit. I found that Premiere Pro installs a good AC3 encoder that can be accessed from Graphedit. But ATM I cannot remember how I got it going under non Premiere Apps. (Will think about it).

[Yakomo]

Ok, I created the AC3 using the above settings. Is there a way to check if the DOlby Surround flag has indeed be set? The DelayCut Log looks exactly like the AC3 from the DVD Recorder (which of course has not set the Dolby Surround flag):

====== INPUT FILE INFO ========================
File is ac3
Bitrate (kbit/s) 256
Act rate (kbit/s) 256.000
File size (bytes) 170146816
Channels mode 2/0: L+R
Sampling Frec 48000
Low Frec Effects LFE: Not present
Duration 01:28:37.088
Frame length (ms) 32.000000
Frames/second 31.250000
Num of frames 166159
Bytes per Frame 1024.0000
Size % Framesize 0
CRC present: YES
=============================================
====== TARGET FILE INFO ======================
Start Frame 0
End Frame 166158
Num of Frames 166159
Duration 01:28:37.088
NotFixedDelay 0.0000
=============================================



And Mediainfo:

Audio #0
Count : 41
Count of stream of t : 1
Kind of stream : Audio
StreamKindID : 0
Codec : AC3
Codec : AC3
Bit rate : 256000
Bit rate : 256 Kbps
Bit rate mode : CBR
Channel(s) : 2
Channel(s) : 2 channels
Sampling rate : 48000
Sampling rate : 48 KHz
SamplingCount : 255220224
Delay : 0
ChannelPositions : L R

[tebasuna51]

Try with this tool (http://www.sendspace.com/file/ffoctb)

[Yakomo]

Wow, great tool tebasuna51! Yes, this looks much better:

File ........: D:\whatever.ac3
Size ........: 170146816 bytes

----------------------------------------- First Frame Info
SampleRate ..................: 0 (48000 KHz)
BitRate .....................: 12 (256 Kb/s)
Version (bsid) ..............: 8 (Standard)
Bit Stream mode (bsmod) .....: 0 (main audio service: complete main, CM)
Audio coding mode (acmod) ...: 2 (2/0 - L, R)
Dolby Surround Mode .........: 2 (Dolby Surround encoded)
Low frequency effects channel: 0 (Not present)
Dialogue normalization ......: - 31 dB
RF atenuattion ..............:-0,28 dB Frame: 1
Languaje ....................: 0 (Not present)
Audio Production Info .......: 0 (Not present)
CopyRight bit ...............: 0
Original bit ................: 0
Timecode1 ...................: 0 (Not present)
Timecode2 ...................: 0 (Not present)
Additional Bsi ..............: 0 (Not present)
Block switch flags ..........: 0
Dither flags ................: 3
Dynamic Range Info ..........: 0 (Not present)
--------------------------------------------- Revised Info
RF Ov. Pr. min/max : -11,52 /-0,28 dB
Dyn. Range min/max : -0,42 /-0,14 dB
Total Frames ......: 166159
Duration ..........: 5317,088 seconds. ( 1 h. 28 m. 37,088 s.)
------------------------------------------------- End Info