- Posts: 1
- Joined: Mon Apr 08, 2019 8:42 am
- Real Name: Adrian Roe
We have 4 independent examples where we occasionally see the audio and the video on the SDI capture from a Decklink go out of sync - sometimes by up to several seconds. We have seen this on 4 separate encoders (2 running on Linux, two on Windows (one of them GraphEdit)).
We are confident that the drift is caused by an issue in the upstream SDI (for example one case immediately followed a power outage to an upstream mixing desk) but we really need to be able to detect and deal with the issue.
We've written low level test code that just dumps the raw audio / video data and corresponding PTS directly to disk exactly as it come out of the BMD API and it is clear that the raw data is wrong (i.e you get both audio and video frames delivered with near identical PTS values that should in fact be a few seconds apart). For "problematic sources" over time we've had sources go up to about 3 seconds out...
Is there an internal audio buffer that might be queueing content when problematic sources are processed (maybe the CRC of some of the video data is bad, but the audio is still queued and output once a "good" video frame shows up, introducing lag each time that happens?) .
We have seen repros of the issue with a Blackmagic HDMI to SDI converter as input into the Decklink card, so that might be something you could use for testing...
We have tried latest drivers etc (11.1.0.0 from 29.03.2019) but the issue is still present.
Any help very much appreciated!
We are confident that the drift is caused by an issue in the upstream SDI (for example one case immediately followed a power outage to an upstream mixing desk) but we really need to be able to detect and deal with the issue.
We've written low level test code that just dumps the raw audio / video data and corresponding PTS directly to disk exactly as it come out of the BMD API and it is clear that the raw data is wrong (i.e you get both audio and video frames delivered with near identical PTS values that should in fact be a few seconds apart). For "problematic sources" over time we've had sources go up to about 3 seconds out...
Is there an internal audio buffer that might be queueing content when problematic sources are processed (maybe the CRC of some of the video data is bad, but the audio is still queued and output once a "good" video frame shows up, introducing lag each time that happens?) .
We have seen repros of the issue with a Blackmagic HDMI to SDI converter as input into the Decklink card, so that might be something you could use for testing...
We have tried latest drivers etc (11.1.0.0 from 29.03.2019) but the issue is still present.
Any help very much appreciated!