DecklinkCapture Directshow sample fails to save recording

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  • Joined: Wed Jun 26, 2019 9:26 am
  • Real Name: Maja Bojarska

DecklinkCapture Directshow sample fails to save recording

PostTue Aug 20, 2019 12:13 pm

Platform: Windows 10 x64, build v10.0.18362.0
IDE: Visual Studio 2019
Blackmagic hardware related to the encountered issue: Intensity Shuttle USB3.0
Input signal: 720p50, 720p60, 1080p30 over HDMI IN.
MFC and MSVC version: v142
Desktop Video SDK version: 11.2
Desktop Video version: 11.2


I’ve been using an application that’s based on the DecklinkCapture sample, from the Desktop Video 11.2 SDK for Windows (Win\DirectShow\Samples\DecklinkCapture). It works very well with the Decklink Mini Monitor 4K, with various input video formats. However, I wanted to try a different capturing setup using the Intensity Shuttle USB3.0. I encountered some problems regarding saving the encoded AV stream to a file. More specifically, the output file is always 128KB in size, no matter the input format, recording duration, or compression choice.

To find out the root cause of the issue, I tested if this bug arises also with the precompiled “DecklinkCapture.exe” binary file that’s shipped with the aforementioned SDK. The precompiled binary saves the captured video without any problems. As the next step, I compiled the (unmodified) source code for the same application, but using the latest toolset provided by Microsoft (MFC & MSVC v142, Win10 SDK v10.0.18362.0). This time the application failed, in the same way as before (corrupted output file, 128KB in size). The only variable that has changed in the process, is the toolset. Because of this, I believe it is reasonable to assume that it’s the toolset that’s causing the bug.

General observations:
• No problems were encountered while capturing with Blackmagic Media Express
• This issue has been recreated on two other machines (same platform, drivers, etc.)

More observations on unmodified code compiled using the new toolset:
• The video preview still works after setting the target input device and format.
• This issue is non-existent while using the Decklink Mini Monitor 4K.
• Visual Studio doesn’t let me install older versions of the toolsets and insists on upgrading the project to newer versions.

Is there anything that can be done to make this setup work?

Best regards,
Working preview, so capturing the input AV stream works properly.
gui_1.1.0.png (120.33 KiB) Viewed 824 times
Captured AV signal parameters. Used DecklinkCapture sample recompiled with new toolset.
image2019-8-14_12-49-12.png (180.85 KiB) Viewed 824 times

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