How to Save Extracted Frames from Deepstream Pipeline to Video Using OpenCV

Описание: Learn how to resolve issues with saving frames extracted from Deepstream pipeline to video files using OpenCV, including common mistakes and solutions.
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Saving Frames Extracted from Deepstream Pipeline to Video Using OpenCV

If you're working with NVIDIA's Deepstream SDK, you might find yourself wanting to extract frames from a video stream and save them into a video file using OpenCV. However, it's not uncommon to encounter issues, such as creating a video file that doesn't play correctly or is unrecognizably small (like the 9KB file you may have seen). In this guide, we’ll help you troubleshoot this problem and guide you through the necessary steps to save your frames correctly.

Understanding the Problem

You have a working code that extracts frames during the probe function, saves them to a queue, and later attempts to write these frames to a video file. However, the output video is invalid or unplayable. This typically happens due to frame dimensions mismatches or the presence of unsupported formats in video encoding.

Common Issues in Saving Video

Frame Size: One of the primary reasons for a video file not playing correctly is that the cv2.VideoWriter expects frames to be of a specific size. If the frames provided to it are not precisely the same size as specified during the creation of the VideoWriter, it might skip those frames, resulting in a broken video file.

Frame Format: Another issue arises from incorrect color space conversion. Video formats typically do not support alpha channels (the 'A' layer in RGBA), and this can cause encoding errors.

Solution Framework

Step 1: Resize the Frames

Ensure that each frame you write to the video file has the correct dimensions as expected by the VideoWriter. This means you must resize each frame before writing it.

Here's how you can implement this:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Correct Color Conversion

Ensure you are removing any unnecessary alpha layers. Convert the color format correctly before writing to the video file. Instead of using cv2.COLOR_RGBA2BGRA, which keeps the alpha channel, use cv2.COLOR_RGBA2BGR, which removes it.

Here’s how to achieve this:

[[See Video to Reveal this Text or Code Snippet]]

Or, if you prefer to use NumPy, you can directly slice the array to keep only the BGR layers:

[[See Video to Reveal this Text or Code Snippet]]

Step 3: Ensure Proper Initialization of VideoWriter

Make sure you have initialized your VideoWriter correctly with a suitable codec and frame rate. Here is a concise version of the code you should use for initialization:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

Following the above steps should help you successfully save frames extracted from a Deepstream pipeline into a video file using OpenCV. Ensure that you're resizing frames correctly and converting them into the appropriate color format before trying to write them to your video output.

If you've followed all the steps above and are still encountering issues, double-check your frame extraction process and ensure you're indeed capturing valid frames from your video stream. Resolving these common mistakes will help ensure that the process runs smoothly, resulting in a playable video file.

By addressing the resizing and color format issues, you can avoid creating unplayable video files and simplify the video creation process in your projects. Happy coding!