# Eac3to/FAQ
## Before Starting
### Q: I'm a total noob. I don't know how to use command line programs, but i still want to use eac3to

A: There's an unofficial GUI (Graphical User Interface) for eac3to, made by The_Keymaker. It will let you use the program like ordinary windows applications. The latest version of eac3toGUI can be found here.

### Q: I don't want to buy any software. Can I still use eac3to?

A: As described in the How to Use section, you need some commercial software for best quality audio decoding. Although, eac3to supports free libav decoding for all important audio codecs (AC3, E-AC3, TrueHD, MLP, DTS) with full 24 bit output. There's also one important limitation in the libav decoder: DTS-HD information is ignored, which means only the standard DTS core is decoded from all DTS-HD tracks. In addition, DTS decoding is limited to max 5.1 channel decoding (more channels are simply ignored). So for best DTS(-HD) decoding, Sonic is still the preferred decoder.

### Q: I don't like Nero at all, but i would install it to get its decoders. How to minimize the effect?

A: Nero is a big package that contains a lot of separate programs. If you just want to use its decoders, you can install Nero ShowTime only and of course to register the plug-in.

### Q: Why I can't use Nero 8 with eac3to?

A: Nero 8 won't work with eac3to because Nero 8 doesn't allow its DirectShow filters to be used from outside of Nero ShowTime. Nero 7 already tried to prevent other applications from using the DirectShow filters, but eac3to can only use them by some tricks. Nero 8 is now even stricter, so currently there isn't a way to get around these restrictions. This means that you must use/install Nero 7 if you want to use Nero DirectShow filters in eac3to.

### Q: What are the alternatives if I have Nero 8 already installed?

A: If you must have Nero 8 installed then you can use the libav decoder instead of Nero 7. By doing so, the AC3 & E-AC3 decoders might be at a small disadvantage quality-wise compared to Nero, but the difference is probably rather small. TrueHD decoding shouldn't be a problem anyway, as eac3to uses the libav decoder as default decoder. Otherwise, for best AC3 & E-AC3 decoding today you still need Nero 7 with the Blu-ray/HD DVD plug-in.

### Q: Where can I find the "Sonic Cinemaster Audio Decoder 4.3" DirectShow filter?

A: That's a difficult question! The decoder was available through Sonic Cineplayer HD DVD Decoder pack, which seems to be a discontinued product now. It would appear that the only way to access this decoder is though Sonic Scenarist which is rather expensive. Another possible solution could be Sonic Cinevision, but can't be sure the decoder is included. Price is a minus there too.

### Q: Should I replace .dll filters that come with eac3to package?

A: Well, to play safe you should use the ones that ship with eac3to. You can update Aften.dll and libflac.dll with newer versions or cpu optimized builds, but that's not recommended, as they are not well tested. The only decoder that you must never replace is the libav decoder, as it's specially modified to work with eac3to.

## Audio Processing
### Q: eac3to can't recognize my .mpa file

A: Usually, audio tracks get this extension by the application used to demux them. mpa is not the actual extension of the audio track, but just a general extension used for audio tracks. eac3to will recognize correctly all audio tracks with .mpa extension, unless you feed it with a PCM / RAW track. In this case you have to manually change the track's extension to the real one (.pcm or .raw - it's the same).

### Q: Why eac3to doesn't show any bit depth info for AC3 and E-AC3, tracks?

A: Because there's no such thing as bit depth in these formats. They don't have a bit depth parameter. We can only say that these formats decode to 16 bit or 24 bit files, but that's decoder dependable. All decoders eac3to uses decode to 24 bit.

### Q: Why eac3to doesn't show any bitrate info for TrueHD, DTS-HD Master Audio and FLAC tracks?

A: All these audio formats use lossless compression and a variable bitrate, not a constant one. So there's no point to show anything regarding this.

### Q: Can eac3to encode a DTS-HD track to 1536 kbps DTS track?

A: Well, this isn't needed. Encoding a DTS-HD track to 1536 kbps DTS doesn't make sense, because all DTS-HD tracks contain a standard 1536 kbps 5.1 DTS core in them. Simply use the -core switch to extract it.

### Q: I have a 768 kbps DTS track which has the same size as a 1536 kbps DTS track of the same duration. How is this possible?

A: When encoding DTS tracks using Surcode outside eac3to, the output file is padded. This means that while only 768 kbps are used to store audio data, the rest 768 kbps are padded with zeroes, ending up with a 1536 kbps file. This behavior is completely useless and does nothing but consuming space. All DTS tracks you get from DVD, HD DVD or Blu-ray are in compact form. Also that's what all freeware software packages (which can handle DTS) expect. To remove the padding from a DTS track, you can simply run it through eac3to using the eac3to input.dts output.dts command.

### Q: How do I check whether a TrueHD track is 16, 20 or 24 bit?

A: Every TrueHD track has a bit-depth of 24 bit. Every one. Every TrueHD decoder always outputs 24 bit. However, here comes the big key: Most times, only some of those 24 bits are filled with real audio data and the rest is just zeroed out. This means that some TrueHD tracks contain full 24 bit of information, while others have 4 bit or 8 bit of those 24 bit filled up with nothing but zeroes. eac3to detects both situations and behaves accordingly. It will never throw away any audio data when doing a conversion, unless you explicitly tell it to.

### Q: I get "track contains more than 16 bit of information" but file size is too small for 20 or 24 bit. What's wrong? not ok

A: There are audio tracks (like the PCM track from The Pirates of the Caribbean: The Curse of the Black Pearl Blu-ray Disc) which have a really weird bit depth: Most of the track has only 16bit of the 24bit filled with data, while the remaining 8bit were always zeroes. But there are a few (very few) parts of the audio track where suddenly those 8bit have data in them.

## Container Processing
### Q: How to demux an EVO, VOB or AOB file to a different directory?

A: eac3to's automated demuxing with -demux switch doesn't accept any output files. The demuxed files are always written in the input's file(s) directory. To demux to a different directory, see Container Format examples.

## Movie Processing
### Q: Whatever i tried, i can't mux audio and video together. Why?

A: This is intended. eac3to presently just muxes the video to MKV and leaves audio muxing to you, because maybe you also want to mux additional audio tracks from DVD or subtitle tracks. eac3to cannot handle all that. In addition, maybe someone wants to specify languages for each audio / subtitle track.

## Troubleshooting
### Q: What does "Nero Audio Decoder is not working correctly" message mean?

A: You get this error message when typing the eac3to -test command. It means the Nero Blu-ray / HD DVD plug-in is not registed. There isn't something you need to install in adittion to the main Nero package. Just buy and register the plug-in. Without this you can't use the Nero decoders.

### Q: What does "Getting Nero Audio Decoder 2 instance failed" message mean?

A: It means the Nero decoder isn't installed on your pc. You have to install Nero 7 and also buy the Nero Blu-ray / HD DVD plug-in to make Nero decoders to work.
Some people, however, still receive this error even after installing Nero 7 Ultra and the Nero Blu-Ray / HD DVD plugin.
To make sure your plugin is actually installed - for Windows check OS Drive:\Program Files (x86)\Common Files\Ahead\DSFilter and ensure you have the following file:
* NeAudio2.ax
A lot of users experiencing this issue even after installing Nero 7 (me included) noticed that NeAudio2.ax is never installed in some Nero 7 installs or the Blu-Ray / HD DVD plugin did not install this correctly.
Make sure these are there then proceed to open a command prompt (elevated Admin prompt) and re-register NeAudio2.ax
regsvr32.exe (Location of NeAudio2.ax).

### Q: "The Sonic Audio Decoder doesn't decode TrueHD properly". What's wrong?

A: You're getting this error because the Sonic Audio Decoder doesn't decode TrueHD properly! Read Decoding compressed audio for details.

### Q: What does "Track is not clean. Use delaycut to clean it" message mean?

A: This message pops up when eac3to is fed with an audio track which has some corruption in it. It's a common problem problem for AC3 and E-AC3 tracks and it's usually caused by a bad disc rip. Often enough the problem is solved when the disc is re-ripped. Anyway, delaycut (v1.3.0.0) can be used (it supports AC3, E-AC3 up to 5.1ch and DTS files only) to "clean" the track, by removing the corrupted parts. Note, that if the corruption is big, more parts (frames) are removed and an audio / video sync problem is rising.

### Q: "The format of the source file could not be detected"

A: It's similar to the above problem. The corrupted part is at the beginning of the track or there are some "garbage" data in front of the actual audio data that prevent eac3to format detection (usually in DTS files). delaycut (v1.3.0.0) can be used again to "clean" these tracks.

### Q: "The encode button didn't seem to pressed" in DTS encoding with Surcode

Surcode sais/asks: "At least one valid source file must be specified to encode.". Closing Surcode... Pressing the Surcode "Encode" button didn't seem to work...
Surcode doesn't like long filenames/paths. Change them and you 'll be ok (assuming -test is working).

### Q: I came across a troublesome file. How to make a sample to send for testing?

A: A sample is made by cutting a small piece from the original troublesome file. There are 2 ways (plus 1 more for HD DVD EVO files only) to make a sample. The first way is to use a hex editor (like the free HxD one). The second is to use drmpeg's command line tools. The 3rd way, which applies only to EVO files, is more complicated: Load the troublesome file to Pelican9's EVOdemux, press rebuild (select only the streams you want) and cancel the process after a while.
Samples of 20 MB to 50 MB, depending on the file type should be big enough. If you're encountering a problem with a container file, cut a sample from it, but not from the demuxed streams in it. The sample must be from the beginning of the file. On the contrary, audio samples should contain the specific part that gives the problem. Look at the eac3to's progress bar when the error or crash is occurred to figure out that point. In any case you have to be able to reproduce the problem with the sample. Otherwise it's useless.
Once the sample is made, it can can be uploaded to a filesharing site, or anywhere it's convenient. The link to it should be posted in eac3to's official thread in doom9 forum.