I was wondering, is there any way to replaygain video files? Take, for example, multiple episodes of a series that you want to watch in series but they are compressed with different audio codecs in the files. MPEG AUdio, Windows Media, OGG. Does any solution exist? If not, what would be the technical barriers to creating one?

Destron

Well, for starters a ReplayGain-enabled DirectShow decoder filter (or decoder software if you're on Linux) would be nice.

But demuxing the audio stream, replaygaining it, and remuxing it with video would certainly work. For example, you could extract a MP3 track from a video file, run it through MP3Gain and remux the now replaygained MP3 track with the video.

The problem with non-MP3 formats is that you would need to adjust the gain on the audio data itself; no decoder filter that I know of supports ReplayGain tags. I don't know whether that's possible with Vorbis without re-encoding. WMA would have to be decoded, replaygained and then re-encoded with huge quality loss, naturally.

A nice solution would be a fb2k-like video player that would store the ReplayGain values of video files in a database, without the need to modify the video files at all.

I generally use Besweet (via Oggmachine gui) when I rip dvd's, when applying gain it stores gain info in the tags which is read by the oggds filter.
I'm pretty sure it does something similar for mp3's but I always use ogg so I'm not totally sure.
You can find more info @ doom9.

Thanks for the input. Yes, I use BeSweet also, but the problem is with files that I did not make myself. The best solution would probably be replaygain tags in the container. This would be perfect for MKV since the standard is not yet set in stone.

I encode a lot of Vorbis Xvid OGMs using vorbis gain. It sounds great comparing to those poor (i mean quiet) sounding mp3 AVIs I used to produce.

The matroska specs show a replay gain field since the very beginning already, but unfortunately there are no tools writing the element yet, leave alone reading it. The problem, as mentioned above, was to make a replay gain DirectShow filter to support this for the most used matroska players. Integrating into matrix mixer filter or morgan stream switcher sound like feasible alternatives to me .....