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Trouble streaming and recording at the same time

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Blaise Douros
Trouble streaming and recording at the same time
on Jun 3, 2014 at 5:22:37 pm

Hey all,
I've got a ticket open with Telestream support about this, as well as a forum post at Telestream, but thought I'd tap the Cow forums as well to see if anyone else has seen this issue.

My system:
Wirecast 5.0.3

Hewlett Packard z240 workstation
Windows 7 Pro 64-bit, SP1
Xeon 4-core processor at 3.6 GHZ
NVIDIA Quadro 1 GB graphics card
Matrox VS4 SDI input card
Boot drive: ATA Western Digital 500 GB (10% capacity used), Bus 0
Separate 4 TB internal RAID 0 for pre-recorded media: two 2 TB drives (10% capacity used), Bus 4
Streaming to Ustream servers
Speedtest: 15 mbps downstream, 2.15 mbps upstream
Pingtest: 68 ms ping, 10 ms jitter

Video sources:
- Two HDMI cameras fed into Blackmagic HDMI-to-SDI converters, connected to Matrox capture card.
- Prerecorded video, stills, and lower thirds running off internal Raid 0
- Audio coming in from two wireless mics via Tascam DR-100 mkII, connected to system audio line-in via 3.5mm

Wirecast Prefs:
Video Display Rate: 30 fps
Live Icons: On

Use High Quality Video: On
Render YUV with gfx card: Off
Disable Vertical Sync: On

Wirecast Canvas Size: 720p

Broadcast codec:
30 fps
Avg Bitrate: 600 kbps
Quality: 2 (Super Fast Encoding)
Profile: Main
Key Frame every: 240 frames

Stereo, 96 kbps, 44.1

Disk record settings:
H.264 Main
Key frame every: 24
Avg bitrate: 10000

Now, on to the interesting stuff.

My company runs live streamed product announcements on a fairly regular basis; usually monthly. The most recent broadcast was about two weeks ago, and was about 50 minutes long. Everything on my dashboard appeared to go flawlessly. After the presentation ended, we got reports of trouble with the stream, and then a total loss of audio starting around 40 minutes in (I know, I would have liked to get them immediately); streaming viewers had seen either the video stream freezing intermittently, and then at the 40-minute mark, lost audio entirely. I reviewed my line cut from the copy recording to my local drive, and found that at that 40-minute point, the audio on the local copy devolved into digital noise, while the video was fine.

During the broadcast, the CPU never rose above 60%, memory was around 20-30%, and bandwidth was at full bars.

Successive tests have revealed that I cannot seem to stream and record at the same time. The stream works great until I hit the record button, at which point the stream chokes; when I review the local copy of the video, the audio problems begin almost immediately as well. The interesting part is that it has started to happen almost immediately when I hit the record button, whereas during the broadcast, it took some time before it got bad.

I have tried multiple codecs (H.264, MP4), bitrates (everything from 3000 kbps up to 15,000), and wrappers (WMV vs Quicktime), and this does not seem to make much of a difference. WMV is slightly better than Quicktime, and causes a bit less choking, but eventually ends up in the same situation--it just takes a bit longer. Sometimes when I switch to WMV and then back to Quicktime, I can get Wirecast to record video without the audio issues in the recording or killing the stream--however, if I stop and restart the recording, the problem reappears immediately on the second recording (I am giving it 30-60 seconds between stopping and restarting).

The source of the video does not make a difference--the same thing happens whether I'm playing pre-recorded video or running a live feed from the Matrox input.

I have also switched the location of the recorded file between the two internal drives; it makes no difference to the performance whether I record to the boot drive or the RAID 0. I realize a third dedicated drive for recording would probably be better.

In playing with the settings, I am convinced this is not a CPU issue; when recording video at lower bitrates, the CPU can be no higher than 30-40%, and I still see the problem.

Finally, I have tried a few more esoteric steps, like disabling Quicktime's DirectDraw settings in an attempt to free up the video card; this had no effect.

So, the question is, has anyone else had trouble streaming and recording at the same time, and if so, have you found a solution? Anything about my setup strike you as potentially problematic? Wirecast issue, or user error?

I don't have one of these events for another month or so but I want to get this ironed out ASAP; if the exec team loses confidence in these streamed product intros, then they'll pull the plug on them, which makes my job a bit less necessary...

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Blaise Douros
Re: Trouble streaming and recording at the same time
on Jun 4, 2014 at 4:21:52 pm

For anyone interested, I was advised by Craig on the Telestream forums to use an MP4 wrapper for output rather than QT. The Windows QT architecture is shaky enough that Telestream does not recommend using it for 1080p capture of video stream in Wirecast.

This has provided me with a good workaround of Quicktime--I've performed a few tests and it seems to be working well.

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