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KpeX · 8th January 2004, 15:06

10. How can I split and join AAC files?

AAC in MP4:
MP4Box can be used for splitting and joining all MP4 files including those with AAC audio. See this thread for full information.

MP4 with AAC inside can also be edited by QuickTime Pro.

Raw AAC streams:
Raw aac streams (*.aac) can be split and joined by using BeSplit.

Splitting:

Code:

besplit -core( -input in.aac -prefix out -type aac -ending ) -split( 0.0 x.x )

This command-line would cut in.aac into two parts: 0.0 s up to x.x s and x.x s up to the end of the file (-ending).

Joining:
First create a list file, which is a text file listing each file to be joined on a separate line. Then save as join.lst and use BeSplit:

Code:

besplit -core( -input join.lst -prefix out -type aac -join )

AAC streams (*.aac) can also be joined via command prompt:

Code:

copy /b first.aac + second.aac joined.aac

11. What are the pros and cons of the AAC audio format?

Pros:

Low bitrate (with comparable quality to other codecs) and hence low filesize, with SBR in specifications.
Multichannel (up to 48 full bandwidth channels can be implemented)
AAC is the official audio format of the MPEG-4 standard, and future hardware support is very likely.

Cons:

(No standalones that playback AAC are available at this time.) [All devices play fine AAC now, but must have HDMI conexion to AVR's for multichannel]
AAC is heavily patented technology.

12. Is it possible to pass AAC over S/PDIF?

[Still not, but use HDMI to pass PCM multichannel]

It is possible, although it has not yet been fully implemented. Only a few hardware devices currently support AAC decoding, and no DirectShow filter has yet been implemented with AAC pass-through ability. However, this is definitely a possibility for the future. Read more about S/PDIF and AAC hardware support here and here.

However, until AAC over SPDIF becomes more viable, there are several DirectShow filters that can be used to encode six channel AAC to AC3 over S/PDIF on the fly. Dolby Out DS filter by Haaan , as well as 1.x versions of AC3Filter can be used for this purpose. Although this reencoding on the fly process will theoretically result in a quality loss, using the full 640 kb/s bitrate allowed will result in an excellent listening experience and minimal quality loss.

13. How are bitrates divided among channels in 5.1 LC and 5.1 HE AAC? What bitrate should be used for 5.1 AAC to be equvalent in bits/channel to 128kbps?

For the bits/channel to be the same, one must add 2x(bitrate per stereo)(FL,FR,RL & RR)+ 1x(mono bitrate(Centre))+ a small additional bitrate for lfe. Therefore the total bitrate should be about 2.5-3x as much as stereo to achieve the same bits/channel. So to achieve the datarate equivalent to 128kbps stereo: 128kbps*2.5=320 kbps. 320kbps is a good quality bitrate for LC AAC. However due to the efficiency and channel coupling of AAC, one can encode HE-AAC at 128kbps and still have decent quality and 5.1 channels.

14. At what bitrates is the HE-AAC profile used in Nero?

[NeroAacEnc output AAC-HE at -q 0.31
The rest of FAQ's are usseless now.]

For CBR settings, 96kbps and below use HE-AAC. For VBR settings, streaming profile and below can produce HE-AAC. If your input source is 5.1 aiff , then HE AAC can be produced at 128kbps using Nero only.

15. What gain setting should I use to encode AAC with BSN/Oagmachine?

Eventhough BeSweet/Bsn has implemented Hybrid gain, there are no Directshow filters capable of using the hybrid gain information at this time. So it is not recommended at the moment. Instead use normalization or pregain.

16. Is there any AAC ACM codec that can be used with VirtualDub?

There is currently no ACM AAC codec due to AAC and AVI not being completely compatible. In the FAAC project this was once attempted and never finished.

17. Encoding doesn't start with Besweet/Nero, i have installed all the BeSweet and Bsn files. Please help?

For BeSweet/BSN/Oagmachine/BeSweet GUI to encode Nero AAC, three dlls from a valid nero installation are needed: 'aac.dll', 'aacenc32.dll' and 'NeroIPP.dll'. These dlls need to be put in the BeSweet folder. From version 60023 onwards aac.dll and aacenc32.dll check for the NeroIPP dll in the registry, therefore a valid Nero Ultra Edition or NeroMix installation is needed.

18. I cannot see the Nero encoding GUI when encoding with OagMachine/BeSweet, how is it activated?

In Oagmachine, under the AAC encoding option, check "show configuration dialogue". If you are using command line, then add a '-config' to the '-bsn' section.

19. Why is my ac3/dts encoded at 48Khz in Oagmachine/BeSweet GUI slow when played back?

That's because you're probably using an old build of BeSweet, since the bug had been fixed in bsn.dll v0.21 (bundled with BeSweet). Check your BeSweet logfiles to make sure you have bsn.dll v0.21.
More info on the old bug :
The Nero encoder expects specific sample-rates depending on the bitrate, profile, and number of channels. When encoding using BSN earlier than v0.21, the internal nero resampler is not used and you must feed the Nero encoder with the correct sample rate. See this thread to determine your correct sampling rate and a more thorough explanation by bond.

20. How can I ensure my encoded AAC is HE and not LC?

Use the CoreAAC DirectShow filter properties to check "AAC+SBR". Foobar2000 also shows the same.
In the 3ivx audio decoder config it is shown as HE-AAC.

21. What switch for multichannel should be used in Oagmachine/BeSweetGUI when using the 600X nero plugin?

Use -6chold for nero plugins earlier than or equal to v6.0011(old). Above 6.0011 use -6chnew.

22. My Nero encoded HE-AAC contains popping noises, what did I do wrong?

This problem occurs when you enable PNS in the Nero encoding GUI. Uncheck the PNS option to get rid of the problem.

23. Are there any recommendations for encoding with good quality with FAAC?

Yes, see the FAAC wiki and also this discussion on FAAC 5.1 encoding.

24. How can I convert AAC to WAV or AC3?

First you should read both this document and the AC3 FAQ to learn about the concepts and tools available. However if you still need a walkthrough, see this guide or this graphedit guide by magicclue.

25. Where can I find more information about AAC?

Audiocoding Wiki
Coding Technologies
Dolby

8th January 2004, 15:06	#10 \| Link
KpeX Registered User Join Date: Jun 2003 Location: Great Lakes, USA Posts: 1,433	10. How can I split and join AAC files? AAC in MP4: MP4Box can be used for splitting and joining all MP4 files including those with AAC audio. See this thread for full information. MP4 with AAC inside can also be edited by QuickTime Pro. Raw AAC streams: Raw aac streams (.aac) can be split and joined by using BeSplit. Splitting: Code: besplit -core( -input in.aac -prefix out -type aac -ending ) -split( 0.0 x.x ) This command-line would cut in.aac into two parts: 0.0 s up to x.x s and x.x s up to the end of the file (-ending). Joining: First create a list file, which is a text file listing each file to be joined on a separate line. Then save as join.lst and use BeSplit: Code: besplit -core( -input join.lst -prefix out -type aac -join ) AAC streams (.aac) can also be joined via command prompt: Code: copy /b first.aac + second.aac joined.aac 11. What are the pros and cons of the AAC audio format? Pros: Low bitrate (with comparable quality to other codecs) and hence low filesize, with SBR in specifications. Multichannel (up to 48 full bandwidth channels can be implemented) AAC is the official audio format of the MPEG-4 standard, and future hardware support is very likely. Cons: (No standalones that playback AAC are available at this time.) [All devices play fine AAC now, but must have HDMI conexion to AVR's for multichannel] AAC is heavily patented technology. 12. Is it possible to pass AAC over S/PDIF? [Still not, but use HDMI to pass PCM multichannel] It is possible, although it has not yet been fully implemented. Only a few hardware devices currently support AAC decoding, and no DirectShow filter has yet been implemented with AAC pass-through ability. However, this is definitely a possibility for the future. Read more about S/PDIF and AAC hardware support here and here. However, until AAC over SPDIF becomes more viable, there are several DirectShow filters that can be used to encode six channel AAC to AC3 over S/PDIF on the fly. Dolby Out DS filter by Haaan , as well as 1.x versions of AC3Filter can be used for this purpose. Although this reencoding on the fly process will theoretically result in a quality loss, using the full 640 kb/s bitrate allowed will result in an excellent listening experience and minimal quality loss. 13. How are bitrates divided among channels in 5.1 LC and 5.1 HE AAC? What bitrate should be used for 5.1 AAC to be equvalent in bits/channel to 128kbps? For the bits/channel to be the same, one must add 2x(bitrate per stereo)(FL,FR,RL & RR)+ 1x(mono bitrate(Centre))+ a small additional bitrate for lfe. Therefore the total bitrate should be about 2.5-3x as much as stereo to achieve the same bits/channel. So to achieve the datarate equivalent to 128kbps stereo: 128kbps2.5=320 kbps. 320kbps is a good quality bitrate for LC AAC. However due to the efficiency and channel coupling of AAC, one can encode HE-AAC at 128kbps and still have decent quality and 5.1 channels. 14. At what bitrates is the HE-AAC profile used in Nero?* [NeroAacEnc output AAC-HE at -q 0.31 The rest of FAQ's are usseless now.] For CBR settings, 96kbps and below use HE-AAC. For VBR settings, streaming profile and below can produce HE-AAC. If your input source is 5.1 aiff , then HE AAC can be produced at 128kbps using Nero only. 15. What gain setting should I use to encode AAC with BSN/Oagmachine? Eventhough BeSweet/Bsn has implemented Hybrid gain, there are no Directshow filters capable of using the hybrid gain information at this time. So it is not recommended at the moment. Instead use normalization or pregain. 16. Is there any AAC ACM codec that can be used with VirtualDub? There is currently no ACM AAC codec due to AAC and AVI not being completely compatible. In the FAAC project this was once attempted and never finished. 17. Encoding doesn't start with Besweet/Nero, i have installed all the BeSweet and Bsn files. Please help? For BeSweet/BSN/Oagmachine/BeSweet GUI to encode Nero AAC, three dlls from a valid nero installation are needed: 'aac.dll', 'aacenc32.dll' and 'NeroIPP.dll'. These dlls need to be put in the BeSweet folder. From version 60023 onwards aac.dll and aacenc32.dll check for the NeroIPP dll in the registry, therefore a valid Nero Ultra Edition or NeroMix installation is needed. 18. I cannot see the Nero encoding GUI when encoding with OagMachine/BeSweet, how is it activated? In Oagmachine, under the AAC encoding option, check "show configuration dialogue". If you are using command line, then add a '-config' to the '-bsn' section. 19. Why is my ac3/dts encoded at 48Khz in Oagmachine/BeSweet GUI slow when played back? That's because you're probably using an old build of BeSweet, since the bug had been fixed in bsn.dll v0.21 (bundled with BeSweet). Check your BeSweet logfiles to make sure you have bsn.dll v0.21. More info on the old bug : The Nero encoder expects specific sample-rates depending on the bitrate, profile, and number of channels. When encoding using BSN earlier than v0.21, the internal nero resampler is not used and you must feed the Nero encoder with the correct sample rate. See this thread to determine your correct sampling rate and a more thorough explanation by bond. 20. How can I ensure my encoded AAC is HE and not LC? Use the CoreAAC DirectShow filter properties to check "AAC+SBR". Foobar2000 also shows the same. In the 3ivx audio decoder config it is shown as HE-AAC. 21. What switch for multichannel should be used in Oagmachine/BeSweetGUI when using the 600X nero plugin? Use -6chold for nero plugins earlier than or equal to v6.0011(old). Above 6.0011 use -6chnew. 22. My Nero encoded HE-AAC contains popping noises, what did I do wrong? This problem occurs when you enable PNS in the Nero encoding GUI. Uncheck the PNS option to get rid of the problem. 23. Are there any recommendations for encoding with good quality with FAAC? Yes, see the FAAC wiki and also this discussion on FAAC 5.1 encoding. 24. How can I convert AAC to WAV or AC3? First you should read both this document and the AC3 FAQ to learn about the concepts and tools available. However if you still need a walkthrough, see this guide or this graphedit guide by magicclue. 25. Where can I find more information about AAC? Audiocoding Wiki Coding Technologies Dolby Last edited by tebasuna51; 27th September 2021 at 03:00. Reason: Update