[media] usbtv: improve a comment

/* Copy data from chunk into a frame buffer, deinterlacing the data

/* Copy data from chunk into a frame buffer, deinterlacing the data

 * into every second line. Unfortunately, they don't align nicely into

 * into every second line. Unfortunately, they don't align nicely into

 * 720 pixel lines, as the chunk is 240 words long, which is 480 pixels.

 * 720 pixel lines, as the chunk is 240 words long, which is 480 pixels.

 * Therefore, we break down the chunk into two halves before copyting,

 * Therefore, we break down the chunk into two halves before copying,

 * so that we can interleave a line if needed. */

 * so that we can interleave a line if needed.

 *

 * Each "chunk" is 240 words; a word in this context equals 4 bytes.

 * Image format is YUYV/YUV 4:2:2, consisting of Y Cr Y Cb, defining two

 * pixels, the Cr and Cb shared between the two pixels, but each having

 * separate Y values. Thus, the 240 words equal 480 pixels. It therefore,

 * takes 1.5 chunks to make a 720 pixel-wide line for the frame.

 * The image is interlaced, so there is a "scan" of odd lines, followed

 * by "scan" of even numbered lines.

 *

 * Following code is writing the chunks in correct sequence, skipping

 * the rows based on "odd" value.

 * line 1: chunk[0][  0..479] chunk[0][480..959] chunk[1][  0..479]

 * line 3: chunk[1][480..959] chunk[2][  0..479] chunk[2][480..959]

 * ...etc.

 */

static void usbtv_chunk_to_vbuf(u32 *frame, __be32 *src, int chunk_no, int odd)

static void usbtv_chunk_to_vbuf(u32 *frame, __be32 *src, int chunk_no, int odd)

{

{

	int half;

	int half;