Garbled Audio Issues when Exporting through Blackmagic Decklink
- MacOS 10.15.7
- Wirecast Pro Version 14.0.1 (1265.35e94614)
- Mac Pro (2019), 3.2 GHz 16 core Intel Xeon W, Radeon Pro 580X and W5700X
- Input sources of the video/audio and type of connection used including:
Strictly Rendezvous calls. Replicated the issue when not live with a client by playing a video file on repeat. ProRes 422 1080p. Also replicated with a h264 mp4 file on repeat.
- Mac Pro with Blackmagic Decklink 8k Pro
- Problem occurred with both Livestream and Youtube (separate occasions)
- Wirecast preference settings: https://imgur.com/a/wZTmiGd
- Wirecast Canvas size 1920 x 1080
- Streaming and Recording encoder settings - External encoder: liveU Solo
- Wirecast Output Statistics (CPU%, fps, connection green bars). CPU% was 5-10% at most. fps was steady at 30fps.
So I was streaming for some clients using rendezvous, to connect remote people. The place where I was streaming from had some internet connectivity issues, so I used wirecast "output" to my decklink, sending an SDI signal out. I plugged the SDI cable into a liveu solo, which allows me to bond multiple internet connections together for a more robust stream. I was sending rtmp feed from liveu solo to livestream.com
About 50 minutes into a 60 minute broadcast, the audio started getting very garbled. It was barely noticeable at first, but then kept getting worse and worse. I was recording the event to an external SSD, and there were no issues with the recording at all. But the SDI signal audio was unintelligible. The next day, I streamed a single ~1 minute video on repeat to youtube. The problem repeated itself. Every ~1 hour or so, the audio would become garbled, and get worse and worse. I discovered that I could stop the output, then restart it, and it would be fixed. But I really don't want to stop outputting video and audio in the middle of a live broadcast!
You can see examples of this garbling in the below video. If you skip to 1:43:30, the audio is perfect. Around 1:43:52 it starts to get garbled. Over the next 10 minutes it gets progressively worse. Skip to 1:52:00 and it is barely understandable.
I replicated the above test using Adobe Premiere. I set the playback in Premiere to use the decklink, and dropped the audio into the timeline and just repeated it for hours. The audio never gave me any issues in Premiere, so I'm reasonably sure that this is a Wirecast issue.