Asking for One v4l2-buffer but getting 3


We have a custom CSI Camera that gives YUYV frame. For that I’m using the nvv4l2 camera source for capturing frames When I’m requesting 1 or 2 buffers using ioctl system call ( ioctl(ctx->cam_fd, VIDIOC_REQBUFS, &rb) ), I’m getting 3 v4l2_buffers instead of 1 . I have added a code snippet below. But same when i tried with USB Cam , I’m getting only single v4l2_buffers . Is there is any way to resolve this so that if we ask for one buffer then we should get only 1 v4l2_buffer?

rb.count = 1; // Asking for 1

if (ioctl(ctx->cam_fd, VIDIOC_REQBUFS, &rb) < 0)
ERROR_RETURN(“Failed to request v4l2 buffers: %s (%d)”, // here I’m getting rb.count = 3
strerror(errno), errno);


hello yashrajs,

may I also confirm the JetPack release version you’re running with.
it’s queue 2 buffers internally, buffer N will be released at N+2 frame-start event.
please refer to VI driver, for example,

void tegra_channel_ring_buffer(...) {
        /* release buffer N at N+2 frame start event */
        if (chan->num_buffers >= (chan->capture_queue_depth - 1))
                free_ring_buffers(chan, 1);

Hi Jerry,

I’m using jetpack v 4.6.2

hello yashrajs,

as mentioned above, addition buffers are queued internally.
you may revise the queue depth, or please modify the VI driver accordingly for your use-case,

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