Kodi Community Forum

I have the typical problem...

Bluray rips - I have just used MakeMKV to extract the AC3/DTS soundtrack and uncompressed video are very jerky with the OSD showing pc:24 and the error % rapidly fluctuating with each change of error % manifesting in a frame-jerk. The speed is marked as +0.100%.

The TV does not, unfortunately, support 24p. XBMC is configured to sync playback using the video clock, resampling audio.

What seemed strange to me is that on another TV upstairs, the playback speed is correctly increased to +4.271% (to speed-up 24fps playback to fit into 25fps, I assume - so the frames can be "doubled-up" with no treble/single frames, again, I assume THIS is the cause of the jerks).

I have tinkered with modelines etc - obviously with no success.

But tonight.... I finally worked out my problem. The downstairs XBMC player is connected to a DTS/AC3 compatible amplifier - the one upstairs isn't.

If audio passthru is utilised - the audio is not resampled, the video speed is not increased, the playback is jerky.

I can now change from jerky to perfect playback by unchecking the AC3/DTS options in System/System/Audio and checking the "downmix multiple channels to stereo".

Obviously, however, I lose the 5.1 playback of the AC3/DTS track.

Any suggestions? I can provide debug logs if it will help - but I'm thinking that the lack of resampling for AC3/DTS is by-design (since it is performing AC3/DTS-passthru).

Right, forget alll that - this thread talks about the same issue.

I guess I'll have to try re-encoding my Blueray rips - possibly using AAC?

You can't use 60 hertz? Other than that you could wait until xbmc gets an ac3 encoder (which will probably take months) or set up alsa to do either ac3 encoding or dpl2 downmixing.

Unfortunately not. I haven't investigated why, but when set to 60p, a large number of skipped frames are noted - maybe 300 per minute - and there is no sound at all!

I keep meaning to create a debug log and see what's going on.

HOWEVER, in the meantime - at least i can watch bluray films with smooth playback - even at the expense of 5.1 audio.

I note that gnif is currently working on an AC3 encoder for XBMC - maybe this will allow the resampling and re-encoding of the troublesome stream? Finger's crossed!

I have read several forum posts on the subject of channel re-ordering and confess to being confused!

I currently have MKV files which contain the video stream, and an AC3 or DTS stream 5.1, DD etc.

I have a Revo R3600 so the audio is limited to HDMI.

If I play through XBMC configured with passthru, I get 5.1 surround through my HDMI-capable amplifier - but the picture jerks (for the reasons in the previous posts).

If I disable passthru and enable downmixing, I get stereo sound and the video plays smoothly.

So... is there anything I can do to re-encode the files to make for smooth playback and 5.1? I tried re-encoding with 6 AAC channels but the amp only played the l+r.

I tried installing alsa and configuring it according to this post without success - and tried using the pulseaudio method too. Again, no success, l+r only... in fact - only l+r output when running the speaker test with:-

speaker-test -Dhdmi -c6 -r192000 -FS32_LE

So - any suggestions what I should try? Or was my suggestion that gnif's AC3 encoder may solve my problem? Since, I assume, when playing 24fps source on 50hz screens, XBMC speeds up the source - and if AC3 is disabled and downmixing enabled - it must be decoding the original AC3 and resampling it.... will the AC3 encoder allow this new re-sampled stream to be re-encoded as AC3?

Sorry for all the questions - it's just if gnif's encoder can be used in this way, I'll stop asking and put up with 2-channel sound until the next full release.

Thanks to anyone who can help.

Jon