diff options
| -rw-r--r-- | drivers/media/usb/usbtv/usbtv-video.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/drivers/media/usb/usbtv/usbtv-video.c b/drivers/media/usb/usbtv/usbtv-video.c index 256956b5499c..2a089756c988 100644 --- a/drivers/media/usb/usbtv/usbtv-video.c +++ b/drivers/media/usb/usbtv/usbtv-video.c @@ -265,8 +265,23 @@ static int usbtv_setup_capture(struct usbtv *usbtv) /* Copy data from chunk into a frame buffer, deinterlacing the data * 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. - * Therefore, we break down the chunk into two halves before copyting, - * so that we can interleave a line if needed. */ + * Therefore, we break down the chunk into two halves before copying, + * 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) { int half; |