Buffer length always zero in ffmpeg application in VPSS with v4l2

Please note that in case of user pointer buffer, you will need to allocate the buffers in the user and provide it to the driver. Are you taking care of this?

Regards,

Brijesh

In ffmpeg application,  memory is allocated in mmap_init function.

static int mmap_init(AVFormatContext *ctx)

{

     int i, res;
    struct video_data *s = ctx->priv_data;
    struct v4l2_requestbuffers req = {
        .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
        .count  = desired_video_buffers,
        .memory = V4L2_MEMORY_USERPTR
    };

    res = v4l2_ioctl(s->fd, VIDIOC_REQBUFS, &req);
    if (res < 0) {
        if (errno == EINVAL) {
            av_log(ctx, AV_LOG_ERROR, "Device does not support mmap\n");
        } else {
            av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_REQBUFS)\n");
        }
        return AVERROR(errno);
    }

    if (req.count < 2) {
        av_log(ctx, AV_LOG_ERROR, "Insufficient buffer memory\n");
        return AVERROR(ENOMEM);
    }
    s->buffers = req.count;
    s->buf_start = av_malloc(sizeof(void *) * s->buffers);
    if (s->buf_start == NULL) {
        av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer pointers\n");
        return AVERROR(ENOMEM);
    }

s->buf_len = av_malloc(sizeof(unsigned int) * s->buffers);
    if (s->buf_len == NULL) {
        av_log(ctx, AV_LOG_ERROR, "Cannot allocate buffer sizes\n");
        av_free(s->buf_start);
        return AVERROR(ENOMEM);
 }

 for (i = 0; i < req.count; i++) {
        struct v4l2_buffer buf = {
            .type   = V4L2_BUF_TYPE_VIDEO_CAPTURE,
            .index  = i,
            .memory = V4L2_MEMORY_MMAP
        };
        res = v4l2_ioctl(s->fd, VIDIOC_QUERYBUF, &buf);
        if (res < 0) {
            av_log(ctx, AV_LOG_ERROR, "ioctl(VIDIOC_QUERYBUF)\n");
            return AVERROR(errno);
        }

        s->buf_len[i] = buf.length; //This variable is always zero
        if (s->frame_size > 0 && s->buf_len[i] < s->frame_size) {
            av_log(ctx, AV_LOG_ERROR,
                   "Buffer len [%d] = %d != %d\n",
                   i, s->buf_len[i], s->frame_size);

            return -1;
        }
        s->buf_start[i] = v4l2_mmap(NULL, buf.length,
                               PROT_READ | PROT_WRITE, MAP_SHARED,
                               s->fd, buf.m.offset);

        if (s->buf_start[i] == MAP_FAILED) {
            av_log(ctx, AV_LOG_ERROR, "mmap: %s\n", strerror(errno));
            return AVERROR(errno);
        }
    }

    return 0;
}

Other than this function in v4lc, any where I need to allocate memory for buffers?

Hello,

Rajeshkumar R said:

I had face problem in Memory map allocation, in "dma_alloc_coherent" function.  It had failed to allocate dma memory.

dma_alloc_coherent() returns  pointer to allocated memory on success, NULL on failure

dma_alloc_coherent() is a Linux kernel API.  It allocates memory suitable for a DMA operation.  The memory would come from somewhere in the physical address space that's granted to the Linux kernel via the u-boot bootargs parameter mem=XX.  .  May be is a  problem with insufficient memory. Check how much MB you are passing, may be is not enough.

Rajeshkumar R said:

ffmpeg -vcodec rawvideo -f video4linux2 -pix_fmt yuv422p12be -s 576x720 -i /dev/video0 out.avi

What is the software release that you are using here?

Best Regards,

Margarita

What is the software release that you are using here?

>> I am using the ffmpeg verion 1.1.4.

DMA Failure Log:

ti81xxvin ti81xxvin: hdvpss_map_sub_device_to_input
ti81xxvin ti81xxvin: vidioc_g_std
ti81xxvin ti81xxvin: vidioc_reqbufs
ti81xxvin ti81xxvin: ti81xxvin_buffer_setup
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
ti81xxvin ti81xxvin: vidioc_querybuf
ti81xxvin ti81xxvin: ti81xxvin_mmap
Size 17c000
Size 17c000
Mask 1000000 -1
Dma alocated page
VM No Space
VM return NULL
(NULL device *): dma_alloc_coherent size 1556480 failed
ti81xxvin ti81xxvin: ti81xxvin_release

how to mention buffer size in user application?

Regards,

Rajesh