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Apple QuickTime 6.3 Released, Contains improved AAC codec
Paspro
post Jun 3 2003, 16:36
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Apple just released a new version of QuickTime (6.3) on both Windows and MacOS platforms. According to Apple's web site it contains an improved AAC encoder:

QuickTime 6.3

QUOTE
QuickTime 6.3 delivers extensive support for 3GPP, including video, audio, text, and native .3gp file format support. Because 3GPP is now a part of the core architecture of QuickTime, you can import, export, and play back .3gp files just as you do .mp4 and .mov files. The technologies in QuickTime 6.3 that provide these capabilities are newly enhanced MPEG-4 and H.263 video codecs, a newly enhanced AAC (Advanced Audio Coding) audio codec, a new AMR (Adaptive Multi-Rate) audio codec, a new 3G Text importer and exporter, and a new user-friendly 3GPP export dialog to aid in the creation of 3GPP-compliant files. This support is available via the QuickTime 3GPP Component.


It's time to test the new codec!
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Ivan Dimkovic
post Jun 3 2003, 19:32
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QUOTE
Therefore, the codec is different. Still, if QT is using CBR how come the file sizes are different? Is it possible that QT is using some kind of ABR algorithm with slightly varying bitrates for each frame? Is there any tool which can check the bitrate of each frame


For the 1000000th time - AAC has bit reservoir which is ~9000 bits for 128 K, so CBR files could be different by up to nearly 9 KB.

Each frame can be anywhere between 0 and 6144 bits, multiplied by the number of channels - as long as the CBR bit buffer rules are not violated - if they are violated, file is either ABR or VBR.

So, something like this:

bit_reservoir = (no_of_channels * 6144 ) - (average_bits_per_frame * no_of_channels)

average_bits_per_frame = bit_rate / number_of_frames_per_second


Frame size can be anywhere between max(0, (min_bits_that_do_not_underflow_bit_reservoir)) and min(6144,(max_bits_that_do_not_overflow_bit_reservoir))

So, bit rate is variable locally, as long as the conditions imposed by the bit reservoir are not violated. Bit reservoir is filled when number of bits used is smaller than average bits per frame, and bit reservoir is drained when number of bits used is greater than average bits per frame.

This post has been edited by Ivan Dimkovic: Jun 3 2003, 19:42
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Posts in this topic
- Paspro   Apple QuickTime 6.3 Released   Jun 3 2003, 16:36
- - guruboolez   Poor Roberto... In a few days, a new ahead AAC and...   Jun 3 2003, 16:40
- - Ivan Dimkovic   I can confirm - codec in QT 6.3 is indeed differen...   Jun 3 2003, 17:12
- - richard123   They claim VBR! QUOTE AAC is the new standard...   Jun 3 2003, 17:15
- - rjamorim   Ouch. I wonder if it's the same as in QT 6.2....   Jun 3 2003, 17:19
- - Paspro   QUOTE (richard123 @ Jun 3 2003 - 08:15 AM)VBR...   Jun 3 2003, 17:21
- - rjamorim   Apple fellas are crazy. And clueless.   Jun 3 2003, 17:28
- - guruboolez   QUOTE (rjamorim @ Jun 3 2003 - 05:19 PM)Ouch....   Jun 3 2003, 18:10
- - rjamorim   Interesting... I will probably reencode everythin...   Jun 3 2003, 18:12
- - guruboolez   QUOTE (rjamorim @ Jun 3 2003 - 06:12 PM)I...   Jun 3 2003, 18:14
- - rjamorim   QUOTE (guruboolez @ Jun 3 2003 - 02:14 PM)QUO...   Jun 3 2003, 18:42
- - guruboolez   QUOTE (rjamorim @ Jun 3 2003 - 06:42 PM)It se...   Jun 3 2003, 18:49
- - Paspro   Since I am a MacOS X user, I did a comparison betw...   Jun 3 2003, 19:22
- - Ivan Dimkovic   QUOTE Therefore, the codec is different. Still, if...   Jun 3 2003, 19:32
- - rjamorim   hello, guruboolez. Check it here: http://www.hydr...   Jun 3 2003, 21:45
- - yourtallness   I suppose aac encoding is a feature of the pro ver...   Jun 3 2003, 21:46
- - bond   QUOTE (yourtallness @ Jun 3 2003 - 09:46 PM)I...   Jun 3 2003, 21:47
- - danchr   QUOTE (yourtallness @ Jun 3 2003 - 09:46 PM)I...   Jun 3 2003, 23:06
- - rjamorim   QUOTE (danchr @ Jun 3 2003 - 07:06 PM)You can...   Jun 3 2003, 23:33
- - danchr   AACelerator is nothing but a frontend for QuickTim...   Jun 4 2003, 09:15
- - Paspro   QUOTE (danchr @ Jun 4 2003 - 12:15 AM)AACeler...   Jun 4 2003, 10:05
- - Paspro   On the subject of the quality settings in QuickTim...   Jun 4 2003, 10:16
- - Tripwire   Are there also frontends for Quicktime for the PC?   Jun 4 2003, 11:54
- - Paspro   QUOTE (Tripwire @ Jun 4 2003 - 02:54 AM)Are t...   Jun 4 2003, 14:28
- - JohnV   QUOTE (Tripwire @ Jun 4 2003 - 01:54 PM)Are t...   Jun 4 2003, 14:44
- - Paspro   QUOTE (JohnV @ Jun 4 2003 - 05:44 AM)QUOTE (T...   Jun 4 2003, 14:50
- - rjamorim   QUOTE (JohnV @ Jun 4 2003 - 10:44 AM)http://w...   Jun 4 2003, 16:47
- - danchr   QUOTE (JohnV @ Jun 4 2003 - 02:44 PM)QUOTE (T...   Jun 4 2003, 23:51
- - Mike Giacomelli   QUOTE (JohnV @ Jun 4 2003 - 05:44 AM)QUOTE (T...   Jun 8 2003, 05:49
- - rjamorim   QUOTE (Mike Giacomelli @ Jun 8 2003 - 01:49 A...   Jun 8 2003, 06:15


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