tests: enforce I420 format
Tests are assuming video is I420 with a specific chroma and colorimetry but were not actually enforcing it. Fixes needed as I420 will no longer be the first video format, see gst-plugins-base!689 (merged)
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Tests are assuming video is I420 with a specific chroma and colorimetry but were not actually enforcing it. Fixes needed as I420 will no longer be the first video format, see gst-plugins-base!689 (merged)