Changes between Version 35 and Version 36 of Encode/AAC


Ignore:
Timestamp:
Dec 29, 2014, 8:16:54 PM (3 years ago)
Author:
bp0
Comment:

vbr works well with latest fdk-aac. vbr also works with he-aac, but only in modes 1-3

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  • Encode/AAC

    v35 v36  
    4545=== Variable Bit Rate (VBR) mode ===#fdk_vbr 
    4646 
    47 VBR encoding in libfdk-aac is '''experimental''' and only works with some parameter combinations ([[http://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Issues|details]]). Target a ''quality'', rather than a specific ''bit rate''. 1 is lowest quality and 5 is highest quality. This mode is not compatible with [[#fdk_he|AAC-HE]]. Set the VBR level with the `-vbr` flag. 
    48  
    49 VBR modes give roughly the following bit rates per channel ([[http://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Bitrate_Modes|details]]): 
    50  
    51 ||VBR||kbps/channel|| 
    52 ||1||32|| 
    53 ||2||40|| 
    54 ||3||48-56|| 
    55 ||4||64|| 
    56 ||5||80-96|| 
     47Target a ''quality'', rather than a specific ''bit rate''. 1 is lowest quality and 5 is highest quality. Set the VBR level with the `-vbr` flag. 
     48 
     49'''Note:''' A bug exists in libfdk-aac 0.1.3 and earlier that will cause a crash when using high sample rates, such as 96kHz, with VBR mode 5. ([[http://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Issues|details]]). 
     50 
     51VBR modes gives '''roughly''' the following bit rates per channel ([[http://wiki.hydrogenaud.io/index.php?title=Fraunhofer_FDK_AAC#Bitrate_Modes|details]]): 
     52 
     53||VBR||kbps/channel||AOTs|| 
     54||1||20-32||LC,[[#fdk_he|HE,HEv2]]|| 
     55||2||32-40||LC,HE,HEv2|| 
     56||3||48-56||LC,HE,HEv2|| 
     57||4||64-72||LC|| 
     58||5||96-112||LC|| 
     59 
     60HE bit rates will be much lower. 
    5761 
    5862==== Examples ==== 
     
    7983=== High-Efficiency AAC ===#fdk_he 
    8084 
    81 This is a pair of AAC profiles tailored for low bit rates (version 1 and version 2). VBR mode is not compatible with [[#fdk_he|AAC-HE]] so a bitrate is declared. AAC-HE version 1 is suited for bit rates below 64kb/s (for stereo audio) down to about 48 kb/s, while AAC-HE version 2 is suited for bit rates as low as 32 kb/s (again, for stereo). 
     85This is a pair of AAC profiles tailored for low bit rates (version 1 and version 2). AAC-HE version 1 is suited for bit rates below 64kb/s (for stereo audio) down to about 48 kb/s, while AAC-HE version 2 is suited for bit rates as low as 32 kb/s (again, for stereo). 
    8286 
    8387NOTE: AAC-HE version 2 only handles stereo. If you have mono, or want to down-mix to mono, use AAC-HE version 1.