Friday, November 14, 2008

VideoLAN Client Dynamic Range Compression

A little note on something related to my earlier post.

By default VLC's Dolby decoder follows Dynamic Range Compression (sometimes called DRC) encoded into AC3 files. While this is great for TV's built in speakers and the tinny PC speakers that came with your Packard Bell, that isn't optimal for THX certified home theater systems.

Thankfully it's easy to fix the issue. The following instructions are with respect to VLC 0.9.6.

1. Start up VLC.
2. Click Tools, then Preferences.
3. At the bottom of the Preferences screen, click All.
4. In the left list, click Input/Codecs, Audio codecs, then A/52.
5. Uncheck A/52 dynamic range compression.
6. While you're there, click DCA (stands for DTS Coherent Acoustics, the DTS codec used in DVDs, not to be confused with the Theatrical DTS codec) in the left list, and uncheck DTS dynamic range compression.
7. Click Save.

Now you can enjoy your HDTV/DVDs with a dynamic range you didn't think was possible!

MythWeb buggering on NBC

So a little while ago I wanted to pull up a Chuck I had recorded OTA from our local NBC affiliate using MythTV. Seeing as how my home theater PC is Windows currently (VLC, and therefore Linux can't handle Dolby TrueHD or DTS-HD Master yet unfortunately), I used MythWeb to download the episode to my hard drive, and tried to play it using VLC for Windows.

I was greeted with no audio, and a video track that went through the entire ~hour episode in a matter of minutes. It would show a couple seconds of a scene, then skip forward a number of minutes, rinse and repeat.

I tried downloading the file again, and then tried opening on Linux VLC on a different computer. No go, same issues. A friend of mine who originally got me into MythTV suggested I try reencoding the video using mythtranscode. A bit of research later, and I entered the following command into the Linux command line:

mythtranscode --infile /var/lib/mythtv/recordings/1061_20081110185800.mpg --mpeg2 --showprogress --outfile /home/pcjjman/videos/chuck.mpg

Most of the options are self-explanatory. The --mpeg2 tells mythtranscode to convert the TS stream to a PS stream, and reencode any frames next to commercials. The end result of the operation was the reencoded file played perfectly and I was able to enjoy Chuck in 1080i and 5.1. It also allowed me to skip through the episode using the Alt-Arrow Keys shortcuts in VLC, which didn't work previously.

So if you download a file straight off MythWeb and it's not playing correctly, try reencoding it. It might just do the trick.