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  • S_O
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AC3/DTS Talk
Reply #25
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That's expected. The VBR routine being employed by the test encoder I used just randomizes bitrates. So, some parts of that stream are being encoded at 32kbps.
No, if I remember correctly I limited the min bitrate somewhere. Unfortunately I cannot look it up in the code, my PC is broken (some capicicators on the mainboard are broken). But remember that this patched DLL was created using the old ac3enc which created sometimes non-vaild bitstream anyway, so this doesn´t have to do something with VBR, but the noise you mean is yust artifacts, if it has 128kbps for 5.1, this sounds of course not very good. My VBR-Routine is not normal VBR or ABR, it´s RBR (Random Bitrate).
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Is there a way to convert the ac3 file to a (48kHz) wav file so i can try this anyway? I know this works - i have some 48kHz formatted wav files with ac3 content. Rather inefficient but playable on my system.
Yes, that´s very simple: Install ac3filter and set output to S/PDIF. Open ac3 in GraphEdit (Graph should be: file.ac3 -> AC3 Parser -> AC3Filter -> Sound Renderer). Remove the Sound Renderer and add WAV Dest/File Writer. Press Play and you get a wav file with S/PDIF ac3 data inside. This wav file should be playable in all DirectShow-players, it has FormatTag 0x92. The FormatTag 0x92 will force the soundcard not to apply any change to the data and pass it directly through S/PDIF. But for what do you need that? This is only useable if you want to store 44100Hz AC3-content on a CD. The output played with this wav is exatly the same as if you directly play the ac3 with S/PDIF out.


I also tested this VBR-AC3 on my receiver (Sherwood RD-6106R): No problem, plays prefectly with AC3Filter S/PDIF out. All software decoders except liba52-based and Moonlight Odio Dekoda failed on playing VBR-AC3.

As I have already written in the original thread I don´t see anything in the ATSC A/52 Specs that disallows vbr-ac3, and it seems that the receivers can hadle it yust fine. But is it also allowed on DVD?

  • Latexxx
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AC3/DTS Talk
Reply #26
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edit2: also, i hear film duping houses are going to make/rent prints with SDDS only on demand as they're becoming less and less in demand... (that from a tech's mouth, this year)

At least my local theater uses almost exclusively SDDS even though they have Dolby Digital, DTS, and even a freaky THX sertificate. The only film I remember them showing using some other audio track is Star Wars (NB This information is only based on trailers).

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As I have already written in the original thread I don´t see anything in the ATSC A/52 Specs that disallows vbr-ac3, and it seems that the receivers can hadle it yust fine. But is it also allowed on DVD?


My Philips DVD-722 has on-screen bitrate display and the bitrate of the soundtrack is going up and down all the time. I believe it is ABR.
  • Last Edit: 11 April, 2004, 04:36:54 PM by Latexxx

  • MoOsEb0y
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AC3/DTS Talk
Reply #27
I was able to play the test sample just fine on an Aiwa Dolby Digital Receiver. (Don't know the model, it's not marked) I outputted it using ac3dec in consumer mode on a Linux machine with the SPDIF on the motherboard using a coax connection. Worked just dandily, though I could definately notice the artifacts you mentioned.

  • barnashi
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AC3/DTS Talk
Reply #28
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I did a test at doom9 once: Using a patched ac3enc.dll (thanks to S_O) that outputs VBR streams (it just randomizes the bitrates), I encoded a multichannel stream and tested it with several decoders.

In case someone is wondering, here is the thread:
http://forum.doom9.org/showthread.php?s=&t...&threadid=33966

I can upload the patched AC3enc DLL is someone is interested.

Also, I would like to invite anyone with a receiver to test VBR decoding

This is the VBR stream, from "The Wall" DVD:
http://pessoal.onda.com.br/rjamorim/Test.ac3

You'll notice some times the quality drops badly. You'll understand why if you read the thread at doom9 :B

If you test it, please report:
-Brand and model of receiver
-What you used to send the stream over S/PDIF. I know Moonlight Odio Dekoda can decode VBR, but I don't know if it can send it over S/PDIF.

Thanks.

Regards;

Roberto.
[a href="index.php?act=findpost&pid=157047"][{POST_SNAPBACK}][/a]


Hi rjamorim.
I tested the file you uploaded using winamp 5 with the ac3 plugin (based on ac3filter 0.70 or 1.01, I think it was 0.70). the configuration utility wouldn't let me use s/pdif but when I chose 5.1 channels (2/3 + lfe) I heard the stream fine, in all 6 channels.
also intervideo ac3 filter didn't let me choose the s/pdif mode (it's gray scaled) but when I choose 6 channels all movies ( using ac3 or ac3dvm codec) sounds fine on all 6 channels.

I use Yamaha HTR-5540 reciever connected to the other end of the optical cable.

AC3/DTS Talk
Reply #29
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If you test it, please report:
-Brand and model of receiver
-What you used to send the stream over S/PDIF. I know Moonlight Odio Dekoda can decode VBR, but I don't know if it can send it over S/PDIF.


The stream decodes successfully on my Denon AVR-1601 no funny noises (well obvious decoding errors anyway, not counting artifacts and such)... the synth near the end of the example doesn't seem to be playing any games with respect to bass extension 

I sent the signal via Coax SPDIF through my Hercules Fortissimo III, from Winamp 5, Valex's AC3 Decoder v0.60b

...Although winamp does not correctly report the VBR bitrate
  • Last Edit: 08 July, 2004, 09:37:31 PM by useless_engineer

AC3/DTS Talk
Reply #30
Just played it to my SONY STR-DB780 amp and it went fine.

Using media player classic and the spdif on my extigy and then an optical lead to pipe the ac3 to the amp.

Unsurprisingly the inbuilt ac3 decoder of the extigy chokes and gives lots of skips and silences. I'm wondering if my dvd player's decoder can handle it, ill try and see if it'll read ac3s off a cd, since it reads mp3s.... nope it doesent. If you can up with a quick way to put an ac3 onto a dvd so that a dvd-player would read it I could test it tho. I know it reads movies onto +rw no problem.

JT

  • DeepDose
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AC3/DTS Talk
Reply #31
using PowerDVD on my 5.1 setup.....the Kill Bill DVD in 5.1 DTS is 768kps  ....and sounds amazing