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  • wkmax
  • [*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #100
Hello.

I have one question about VBR encoding in QuickTime. I was searching with Google but have not found detailed explanation of Constrained VBR mode.

Is it better or worse than True VBR? . Maybe it gives higher quality than tvbr only at maximum quality settings (--cvbr 320 VS --tvbr 127) but at lower bitrates I can get better quality with true vbr?


This link might be useful for you:

developer.apple.com/mac/library/technotes/tn2008/tn2237.html
(particularly "encoding properties in detail" section)

Regards
  • Last Edit: 15 February, 2010, 01:34:53 PM by wkmax

qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #101
rpp3po, wkmax, thank you!

Another question: why QT AAC Encoder does not allow to encode at high bitrates (>320 kbps) in CBR mode while in VBR mode it supports frames up to 500 kbps o.0
  • Last Edit: 16 February, 2010, 11:41:28 AM by Steve Forte Rio

  • rpp3po
  • [*][*][*][*][*]
  • Developer
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #102
It's impolite to answer with a counter question, but why should it? It makes sense for VBR in case it encounters super complex passages, but why would one want to force an encoder to such high rates? I even question the sanity of forcing a modern implementation as QT or Nero to not drop below 320 kbit/s.

qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #103
I understand what are you talking about, but I know some people who do not trust the algorithms of choosing bitrates for each frame (complexity detecting algorithms maybe), especially in True VBR mode... And they are not sure of VBR mode safety. And I think that CBR mode with high bitrates will be the safest for the quality despite the fact that it is waste of file size

(sorry for my very bad English)

  • rpp3po
  • [*][*][*][*][*]
  • Developer
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #104
IMHO it is a developer's responsibility to expose reasonable settings for his product, and that does not extend to satisfying feelings as unfounded paranoia. Exposing insane bitrate settings may raise the impression that there might actually be a need for them. If you can present a sample, that would prove otherwise, feel free to share it. People who cannot get over their distrust against lossy compression should go for lossless, anyway, because even extreme bitrates cannot guarantee transparency for 100% of music.

PS BTW, the complexity of the TVBR encoder is actually lower than that of CVBR, ABR, and CBR. What you call "complexity detection" is required for all stages, but the latter must calculate a trade-off against additional constraints.
  • Last Edit: 16 February, 2010, 01:11:43 PM by rpp3po

qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #105
 

Thanks for your answers, it's all as I expected 

best regards

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #106
Important update

Though I said HE-AAC encoder was not available in the Windows version of QT, I've found a way to access the HE-AAC encoder. So, now the latest version has an ability to create HE-AAC files.

--he option enables the HE-AAC encoder. Note that the true vbr mode is not available in this encoder.

Enjoy!

qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #107
Cool!  Thank you.

And does QuickTime have Parametric Stereo technology support ?

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #108
No. HE-AAC v1 only.

  • tedgo
  • [*][*][*][*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #109
Thank you very much .
Is there any "hardcoded" bitrate limit the HE-profile can be used with?

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #110
The limit cahnges according to the samplerate and the number of channel. For example, 80kbps for 44.1kHz, stereo input.

  • tedgo
  • [*][*][*][*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #111
Thanks, i tried it now.
Setting the bitrate higher than 80kbps encodes at 80kbps.
  • Last Edit: 17 February, 2010, 12:03:40 PM by tedgo

  • wkmax
  • [*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #112
Important update

Though I said HE-AAC encoder was not available in the Windows version of QT, I've found a way to access the HE-AAC encoder. So, now the latest version has an ability to create HE-AAC files.

--he option enables the HE-AAC encoder. Note that the true vbr mode is not available in this encoder.

Enjoy!


Excellent!!!, works fine.
Thanks again nao 
  • Last Edit: 18 February, 2010, 03:46:31 AM by wkmax

qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #113
Another questions:

What about 32-bit floating-point input support?

And is it possible to realize two-pass encoding in QuickTime?

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #114
32-bit fp input is already supported. 2-pass encoding is not possible for AAC.

  • rpp3po
  • [*][*][*][*][*]
  • Developer
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #115
It is, Nero supports it. But its kind of senseless. During the good old divx times it made sense to use 2-pass to exactly squeeze a video onto 2 x 700 MB CDRs. 2-pass was the perfect tool, to use up all available storage space up to the last MB. But for AAC it's basically completely senseless.
  • Last Edit: 18 February, 2010, 09:42:49 AM by rpp3po

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #116
It is, Nero supports it.

I should have said "not possible in QuickTime" to be correct.

qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #117
32-bit fp input is already supported.


This is great! Big thank you!

  • b66pak
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #118
@nao how do you explain this?


using qtaacenc-20100212 on a 121 minutes 6ch wav i get 538,097,995 bytes and using qtaacenc-20100218 with the same settings a get 558,822,574 bytes!


encoding line:

Code: [Select]
bepipe --script "import(^rawav.avs^)" | qtaacenc-20100212 --ignorelength --samplerate keep --highest --tvbr 127 - audio.6ch.q127.qtaacenc-20100212.m4a


result:

Code: [Select]
538,097,995 bytes



General
Complete name                    : audio.6ch.q127.qtaacenc-20100212.m4a
Format                           : MPEG-4
Format profile                   : Base Media / Version 2
Codec ID                         : mp42
File size                        : 513 MiB
Duration                         : 2h 1mn
Overall bit rate                 : 589 Kbps
Encoded date                     : UTC 2010-02-18 19:10:27
Tagged date                      : UTC 2010-02-18 19:11:02
Writing application              : qtaacenc 20100212, QuickTime 7.6.5
Encoding Params                  : (Binary)

Audio
ID                               : 1
Format                           : AAC
Format/Info                      : Advanced Audio Codec
Format version                   : Version 4
Format profile                   : LC
Format settings, SBR             : No
Codec ID                         : 40
Duration                         : 2h 1mn
Bit rate mode                    : Variable
Bit rate                         : 576 Kbps
Maximum bit rate                 : 847 Kbps
Channel(s)                       : 6 channels
Channel positions                : Front: L C R, Rear: L R, LFE
Sampling rate                    : 48.0 KHz
Stream size                      : 511 MiB (100%)
Language                         : English
Encoded date                     : UTC 2010-02-18 19:10:19
Tagged date                      : UTC 2010-02-18 19:11:02



encoding line:

Code: [Select]
bepipe --script "import(^rawav.avs^)" | qtaacenc-20100218 --ignorelength --samplerate keep --highest --tvbr 127 - audio.6ch.q127.qtaacenc-20100218.m4a


result:

Code: [Select]
558,822,574 bytes



General
Complete name                    : audio.6ch.q127.qtaacenc-20100218.m4a
Format                           : MPEG-4
Format profile                   : Base Media / Version 2
Codec ID                         : mp42
File size                        : 533 MiB
Duration                         : 2h 1mn
Overall bit rate                 : 612 Kbps
Encoded date                     : UTC 2010-02-18 18:35:26
Tagged date                      : UTC 2010-02-18 18:36:02
Writing application              : qtaacenc 20100218, QuickTime 7.6.5
Encoding Params                  : (Binary)

Audio
ID                               : 1
Format                           : AAC
Format/Info                      : Advanced Audio Codec
Format version                   : Version 4
Format profile                   : LC
Format settings, SBR             : No
Codec ID                         : 40
Duration                         : 2h 1mn
Bit rate mode                    : Variable
Bit rate                         : 609 Kbps
Maximum bit rate                 : 962 Kbps
Channel(s)                       : 6 channels
Channel positions                : Front: L C R, Rear: L R, LFE
Sampling rate                    : 48.0 KHz
Stream size                      : 531 MiB (100%)
Language                         : English
Encoded date                     : UTC 2010-02-18 18:35:18
Tagged date                      : UTC 2010-02-18 18:36:02



best regards
_

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #119
@nao how do you explain this?

Probably the input file has no channel order info (dwChannelMask in WAVEFORMATEXTENSIBLE). The default order was C L R LFE Ls Rs in the version 20100212, but I changed it to L R C LFE Ls Rs in the version 20100217.

  • b66pak
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #120
wrong channel order...you should add to the log file that you fix this!...what is the max rate for multichannel audio?...it has real mutichannel support (2.1, 4.0 etc) or 5.1 ONLY?
_

  • rpp3po
  • [*][*][*][*][*]
  • Developer
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #121
If your source file doesn't include any channel mapping information, there is no such thing as a wrong channel order after conversion. For cases where this information is missing, there is a default ordering proposed by Microsoft, 20100217 uses exactly that.
  • Last Edit: 18 February, 2010, 04:11:33 PM by rpp3po

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #122
what is the max rate for multichannel audio?...it has real mutichannel support (2.1, 4.0 etc) or 5.1 ONLY?

Maximum supported samplerate is 48kHz. Supported multichannel formats are:
  • LC-AAC
    • Quadraphonic (L R Ls Rs)
    • 4.0ch (L R C Cs)
    • 5.0ch (L R C Ls Rs)
    • 5.1ch (L R C LFE Ls Rs)
    • 6.0ch (L R C Ls Rs Cs)
    • 6.1ch (L R C LFE Ls Rs Cs)
    • 7.0ch (L R C Ls Rs Rls Rrs)
    • 7.1ch (L R C LFE Ls Rs Lc Rc)
  • HE-AAC
    • Quadraphonic (L R Ls Rs)
    • 5.1ch (L R C LFE Ls Rs)
    • 7.1ch (L R C LFE Ls Rs Lc Rc)
The result in case the channel order info is missing may be inconsistent.

  • b66pak
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #123
what about max bitrate for multichannel audio?
_

  • nao
  • [*][*]
qtaacenc: a command-line QuickTime AAC encoder for Windows
Reply #124
I forgot to mention, but 8.0ch is also supported. The bitrate limits (@48kHz) are:
  • LC-AAC
    • Quadraphonic : 640 kbps
    • 4.0ch : 640 kbps
    • 5.0ch : 768 kbps
    • 5.1ch : 768 kbps
    • 6.0ch : 960 kbps
    • 6.1ch : 960 kbps
    • 7.0ch : 960 kbps
    • 7.1ch : 960 kbps
    • 8.0ch (L R C Ls Rs Cs Rls Rrs) : 1280 kbps
  • HE-AAC
    • Quadraphonic : 160 kbps
    • 5.1ch : 192 kbps
    • 7.1ch : 256 kbps
The actual limit changes according to the input samplerate.