Universal Media Server | Forum

Hi there,

As the long-winded titled says, I'm having some issues when using the encoded audio passthrough function with my PS3 with many files that use stereo AC3 audio. Essentially, when using just about any form of seeking, audio is lost entirely (to the point where pressing Select only shows stats for video on the PS3, like it's not receiving any audio whatsoever); this occurs with both the PS3's 'scene select' along with the GoTo function. Attempting to use the transcode folder's 'chapter' support yields the same results (even on a fresh restart of UMS, trying just to start the video at the 5 minute mark). Using fast-forward at a low rate (usually 2x or lower is 'safe' from my testing, anything higher is finicky) will preserve the audio. Also, this seemingly has nothing to do with either my basic transcoding quality settings, transcoding buffer size or Java heap size - tweaking those gives me no different results.

After a fair amount of testing, this issue only occurs when working with stereo AC3-encoded audio; DTS works just fine, along with 5.1 AC3. After trying a bunch of files with stereo AC3 audio, I've yet to find anything truly different between files that seek properly and those that don't - bitrate, endianness, etc seem to be a non-factor. I've attached log files (along with MediaInfo logs on the files in question, maybe I'm missing something in the way the audio is encoded that would cause issues?) for 3 test cases: log 1 is of a non-working file, while the other two logs are of files that worked. To test, I'd restart UMS, open the file in question with MEncoder (for whatever reason FFmpeg won't 'do' encoded passthrough on these particular files, it gets sent to my receiver as PCM, implying that the PS3 is handling the audio), let it play for ~10 seconds, and then attempt to skip to 5:00.

Thanks for developing an awesome program so far, it's by far the best media server I've ever tried out!

So after doing a lot of research and tooling around, the issue seems to be related more to the final header/wrapper of the combined audio video file as opposed to the AC3 audio itself. Basically, I extracted the audio from a file that didn't work (through FFmpeg), ran it through eac3to, and put it all back together with FFmpeg - the finished product would seek just fine, so I figured it must have been eac3to's processing. However, the audio file eac3to created was literally identical (down to the checksum level), and simply telling FFmpeg to make a new .avi file (as an example, haven't tried the MKV ones yet) with the 'copy' parameters for acodec and vcodec would create a working file that would seek without losing audio.