[media] gspca - sonixj: Better scanning of isochronous packets
A marker 'ff ff 00 c4 c4 96' indicates an end of frame.
It is 62 bytes long and may be splitted on 2 packets.
It contains a flag 'USB full' which indicates that the frame is truncated.
Signed-off-by: Jean-François Moine <moinejf@free.fr>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/video/gspca/sonixj.c b/drivers/media/video/gspca/sonixj.c
index c414707..21f0330 100644
--- a/drivers/media/video/gspca/sonixj.c
+++ b/drivers/media/video/gspca/sonixj.c
@@ -57,6 +57,8 @@
atomic_t avg_lum;
u32 exposure;
+ s8 short_mark;
+
u8 quality; /* image quality */
#define QUALITY_MIN 60
#define QUALITY_MAX 95
@@ -2787,39 +2789,104 @@
int len) /* iso packet length */
{
struct sd *sd = (struct sd *) gspca_dev;
- int sof;
+ int i;
- /* the image ends on a 64 bytes block starting with
- * ff d9 ff ff 00 c4 c4 96
- * and followed by various information including luminosity */
- /* this block may be splitted between two packets */
- /* a new image always starts in a new packet */
- switch (gspca_dev->last_packet_type) {
- case DISCARD_PACKET: /* restart image building */
- sof = len - 64;
- if (sof >= 0 && data[sof] == 0xff && data[sof + 1] == 0xd9)
- gspca_frame_add(gspca_dev, LAST_PACKET, NULL, 0);
- return;
- case LAST_PACKET: /* put the JPEG 422 header */
+ /*
+ * A frame ends on the marker
+ * ff ff 00 c4 c4 96 ..
+ * which is 62 bytes long and is followed by various information
+ * including statuses and luminosity.
+ *
+ * A marker may be splitted on two packets.
+ *
+ * The 6th byte of a marker contains the bits:
+ * 0x08: USB full
+ * 0xc0: frame sequence
+ * When the bit 'USB full' is set, the frame must be discarded;
+ * this is also the case when the 2 bytes before the marker are
+ * not the JPEG end of frame ('ff d9').
+ */
+
+/*fixme: assumption about the following code:
+ * - there can be only one marker in a packet
+ */
+
+ /* skip the remaining bytes of a short marker */
+ i = sd->short_mark;
+ if (i != 0) {
+ sd->short_mark = 0;
+ if (i < 0 /* if 'ff' at end of previous packet */
+ && data[0] == 0xff
+ && data[1] == 0x00)
+ goto marker_found;
+ if (data[0] == 0xff && data[1] == 0xff) {
+ i = 0;
+ goto marker_found;
+ }
+ len -= i;
+ if (len <= 0)
+ return;
+ data += i;
+ }
+
+ /* search backwards if there is a marker in the packet */
+ for (i = len - 1; --i >= 0; ) {
+ if (data[i] != 0xff) {
+ i--;
+ continue;
+ }
+ if (data[i + 1] == 0xff) {
+
+ /* (there may be 'ff ff' inside a marker) */
+ if (i + 2 >= len || data[i + 2] == 0x00)
+ goto marker_found;
+ }
+ }
+
+ /* no marker found */
+ /* add the JPEG header if first fragment */
+ if (data[len - 1] == 0xff)
+ sd->short_mark = -1;
+ if (gspca_dev->last_packet_type == LAST_PACKET)
gspca_frame_add(gspca_dev, FIRST_PACKET,
sd->jpeg_hdr, JPEG_HDR_SZ);
- break;
- }
gspca_frame_add(gspca_dev, INTER_PACKET, data, len);
+ return;
- data = gspca_dev->image;
- if (data == NULL)
- return;
- sof = gspca_dev->image_len - 64;
- if (data[sof] != 0xff
- || data[sof + 1] != 0xd9)
- return;
+ /* marker found */
+ /* if some error, discard the frame */
+marker_found:
+ if (i > 2) {
+ if (data[i - 2] != 0xff || data[i - 1] != 0xd9) {
+ gspca_dev->last_packet_type = DISCARD_PACKET;
+ }
+ } else if (i + 6 < len) {
+ if (data[i + 6] & 0x08) {
+ gspca_dev->last_packet_type = DISCARD_PACKET;
+ }
+ }
- /* end of image found - remove the trailing data */
- gspca_dev->image_len = sof + 2;
- gspca_frame_add(gspca_dev, LAST_PACKET, NULL, 0);
+ gspca_frame_add(gspca_dev, LAST_PACKET, data, i);
+
+ /* if the marker is smaller than 62 bytes,
+ * memorize the number of bytes to skip in the next packet */
+ if (i + 62 > len) { /* no more usable data */
+ sd->short_mark = i + 62 - len;
+ return;
+ }
+
if (sd->ag_cnt >= 0)
- set_lum(sd, data + sof + 2);
+ set_lum(sd, data + i);
+
+ /* if more data, start a new frame */
+ i += 62;
+ if (i < len) {
+ data += i;
+ len -= i;
+ gspca_frame_add(gspca_dev, FIRST_PACKET,
+ sd->jpeg_hdr, JPEG_HDR_SZ);
+ gspca_frame_add(gspca_dev, INTER_PACKET, data, len);
+ }
}
static int sd_set_jcomp(struct gspca_dev *gspca_dev,