libobs/media-io: Fix copying different line-size video frame

[norihiro]

Description

The outer for loop defines a variable i to indicate the index of the plane, which is as expected.

The inner for loop should use a different name variable. I renamed the variable to y to indicate the line index of the iteration.

Motivation and Context

The PR #10139 implemented to copy a video frame into a different line-size video frame. However, when the line-size was different, the frame was not correctly copied.

I was writing a unit test to cover the new branch introduced by the PR #10139 and realized the bug. Fortunately, the bug has not been released yet.

How Has This Been Tested?

OS: Fedora 38
Tested with a code below.

static void memset_rand(void *dst, size_t size)
{
        long *buf = dst;
        for (size_t i = 0; i < size; i += sizeof(long))
                buf[i] = random();
}
static void video_frame_line_by_line_test(void **state)
{
        UNUSED_PARAMETER(state);

        const int width = 320;
        const int height = 180;
        const int linesize = 328;

        struct video_frame *frame1 = video_frame_create(VIDEO_FORMAT_Y800, width, height);
        struct video_frame frame2 = {0};
        frame2.data[0] = bmalloc(linesize * height);
        frame2.linesize[0] = linesize;

        memset_rand(frame1->data[0], frame1->linesize[0] * height);

        video_frame_copy(&frame2, frame1, VIDEO_FORMAT_Y800, height);

        for (int y = 0; y < height; y++) {
                assert_memory_equal(frame2.data[0] + frame2.linesize[0] * y, frame1->data[0] + frame1->linesize[0] * y, width);
        }

        bfree(frame2.data[0]);
        video_frame_destroy(frame1);

        assert_int_equal(bnum_allocs(), 0);
}

Types of changes

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code has been run through clang-format.
• I have read the contributing document.
• My code is not on the master branch.
• The code has been tested.
• All commit messages are properly formatted and commits squashed where appropriate.
• I have included updates to all appropriate documentation.