ssize_t v4l1_read(int fd, void *buffer, size_t n)
{
int index = v4l1_get_index(fd);
ssize_t result;
if (index == -1)
return SYS_READ(fd, buffer, n);
pthread_mutex_lock(&devices[index].stream_lock);
result = v4l2_read(fd, buffer, n);
pthread_mutex_unlock(&devices[index].stream_lock);
return result;
}
static int v4l2_read_and_convert(int index, unsigned char *dest, int dest_size)
{
const int max_tries = 10;
int result, buf_size, tries = max_tries;
buf_size = devices[index].dest_fmt.fmt.pix.sizeimage;
if (devices[index].readbuf_size < buf_size) {
unsigned char *new_buf;
new_buf = realloc(devices[index].readbuf, buf_size);
if (!new_buf)
return -1;
devices[index].readbuf = new_buf;
devices[index].readbuf_size = buf_size;
}
do {
result = SYS_READ(devices[index].fd, devices[index].readbuf, buf_size);
if (result <= 0) {
if (result && errno != EAGAIN) {
int saved_err = errno;
V4L2_LOG_ERR("reading: %s\n", strerror(errno));
errno = saved_err;
}
return result;
}
result = v4lconvert_convert(devices[index].convert,
&devices[index].src_fmt, &devices[index].dest_fmt,
devices[index].readbuf, result, dest, dest_size);
if (devices[index].first_frame) {
/* Always treat convert errors as EAGAIN during the first few frames, as
some cams produce bad frames at the start of the stream
(hsync and vsync still syncing ??). */
if (result < 0)
errno = EAGAIN;
devices[index].first_frame--;
}
if (result < 0) {
int saved_err = errno;
if (errno == EAGAIN)
V4L2_LOG("warning error while converting frame data: %s",
v4lconvert_get_error_message(devices[index].convert));
else
V4L2_LOG_ERR("converting / decoding frame data: %s",
v4lconvert_get_error_message(devices[index].convert));
errno = saved_err;
}
tries--;
} while (result < 0 && errno == EAGAIN && tries);
if (result < 0 && errno == EAGAIN) {
V4L2_LOG_ERR("got %d consecutive frame decode errors, last error: %s",
max_tries, v4lconvert_get_error_message(devices[index].convert));
}
return result;
}
