How to encode audio to AAC
AAC = Advanced Audio Codec, and it is the preferred audio format in mp4 files
Most newer DVD's have relatively high bitrate audio in .ac3 (Dolby Digital) or .dts format. Sometimes this audio is as high as 1536 Kbps with six or seven channels.
If your source DVD has stereo (2 audio channels) in .ac3 format at 192 Kbps or less (use GSpot or MediaInfo to find out), or if you don't care about the size of your mp4, you can leave the audio unchanged and simply mux it with your x264 video. Technically, you should encode the audio to AAC to comply with the H.264 standard, but many bluray standalone players and software media players will play an mp4 file with .ac3 audio. You might want to make a clip with x264 video and .ac3 audio and test it in your player.
But if the bitrate is any higher, or you want to comply with the H.264 standard to ensure your vid plays in everything it should, or
if you want to reduce the size of your mp4 as much as possible, you can encode to AAC.
MeGUI comes with two AAC encoders (enc_aacplus and faac), but to get the best quality audio, I recommend using Nero AAC Encoder, which is freeware easily found by googling, or you can try this link:
http://www.videohelp.com/download/Ne...odec-1.5.1.zip
Look for the neroAacEnc.exe file (it comes in a "win32" folder). You can put it anywhere you want and then point MeGUI to the file. You may want to create a new folder in the megui/tools folder, call it "nero aac encoder" and put the .exe file in there.
Wherever you put the .exe, you need to point MeGUI to that location.
With MeGUI open, click on the Options menu and choose Settings.
Click on the External Program Settings tab.
At the top, to the far right of neroAacEnc, click on the button with three dots (...) and navigate to the folder where you put neroAacEnc.exe.
Then click Save.
[IMG]http://i45.*******.com/66hr3b.jpg[/IMG]
Downmixing to stereo
If you have multichannel audio (up to 7 channels), and you want to convert it to two channels (stereo), or if your source is already stereo, then read this section. If you have multichannel and you want to keep all the channels, then see the section below "Encoding with multiple channels".
When you downloaded or updated MeGUI, you were given a choice of audio profiles (also called presets), one of which is called "Nero AAC: NDAAC-HE-64Kbps".
[IMG]http://i50.*******.com/bgydjl.jpg[/IMG]
Start on the MeGUI Input tab. If you can find this profile in the dropdown box under Audio/Encoder settings, then click on Config and modify it as follows. If not, then choose Nero AAC: *scratchpad* click Config and modify it like this:
[IMG]http://i46.*******.com/53232c.jpg[/IMG]
When you have tweaked the settings to match the image above, you can click on "Update" to save the new settings to the "NDAAC-HE-64Kbps" profile, or you can click on "New" and give the new preset a name of your choosing.
Just use this preset when encoding your audio, and you will get surprisingly good quality sound at about half the standard bitrate for mp3 (64 vs. 128 Kbps).
Encoding with multiple channels
If your source audio has more than two channels, you can keep all the channels and still reduce the file size by encoding in multichannel AAC.
Just choose one of the profiles that have "MultiChannel" in the name, such as "NDACC-HE-MultiChannel-HQ-192Kbps" - and modify it as above to include Apply Dynamic Range Compression and Normalize Peaks to 98. If you don't have any profiles in your Encoder settings dropdown list with "MultiChannel", then you can use the Nero AAC: *scratchpad* setting and modify it to look like this:
[IMG]http://i47.*******.com/16jkbo8.jpg[/IMG]
Note the differences from "Downmixing to stereo"
- Output Channels = Keep Original Channels
- NeroDigital AAC Options = Adaptive Bitrate @ 192 Kbit/s
When you have tweaked the settings to match the image above, you can click on "Update" to save the new settings to the "NDACC-HE-MultiChannel-HQ-192Kbps" profile, or you can click on "New" and give the new preset a name of your choosing.
Encode it!
Once you have chosen and tweaked the preset, you are ready to begin encoding.
Start again on the MeGUI Input tab. To load the audio file, click the [...] button next to "Audio Input" and navigate to your source audio (.ac3, .dts, .mp2 or .wav). Then click on "Enqueue", move over to the "Queue" tab, and click on "Start".
A Status dialog box will open, showing you the percentage of job that is completed, and when finished encoding, the dialog will close. Your new AAC audio file (with extension .mp4) should be in the same folder as the source, unless you changed the output location in Settings.
See the Yamb tutorial in post #8 above for directions on muxing video and audio.