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i.MX6Q H.264 VPU encoding

Question asked by Simone Cappelletti on Sep 20, 2016

I use the i.MX6Q VPU to decode jpeg image and then encode to h264 file.

The input is a jpeg image with YUV422 color format, whereas i want to encode to YUV420 h264 stream file. For this reasons I use the IPU CSC to convert from YUV422 color format to YUV420.


Therefore the conversion flow is:
1) Decode jpeg image with VPU
2) Convert raw data from YUV422 to YUV420 color format whit IPU CSC
3) Encode raw data converted to h264 stream


I use this libraries / examples to manage easily VPU and CSC:


I think that jpeg image decoding and color format conversion works well. So much so that I tested the raw data images (before and after color format conversion) by this link and all seems ok.

That said, I have problems with h264 encoding.
Reading the h264 encoding flow with VLC I see an overlay green image and I don't know the reasons. Why?!


I attach the raw data images (before and after color format conversion), orignal image and output h264 file.


Thank you to all.




void init(FILE *input_file, FILE *output_file) {
    ImxVpuEncOpenParams open_params;
    ImxVpuRawFrame input_frame;
    ImxVpuEncodedFrame output_frame;
    ImxVpuEncParams enc_params;
    unsigned int output_code;
    long size;
    void *buf;
    ImxVpuJPEGDecInfo info;
    uint8_t *mapped_virtual_address;
    size_t num_out_byte;
    encContex = calloc(1, sizeof(EncContex));
    jpegContex = calloc(1, sizeof(JpegContex));
    jpegContex->fin = input_file;
    encContex->fout = output_file;
    /* Open the JPEG decoder */
    imx_vpu_jpeg_dec_open(&(jpegContex->jpeg_decoder), NULL, 0);
    /* Decode Jpeg and retrive image size */
    /* Determine size of the input file to be able to read all of its bytes in one go */
    fseek(jpegContex->fin, 0, SEEK_END);
    size = ftell(jpegContex->fin);
    fseek(jpegContex->fin, 0, SEEK_SET);
    /* Allocate buffer for the input data, and read the data into it */
    buf = malloc(size);
    fread(buf, 1, size, jpegContex->fin);
    /* Perform the actual JPEG decoding */
    ImxVpuDecReturnCodes dec_ret = imx_vpu_jpeg_dec_decode(jpegContex->jpeg_decoder, buf, size);
    if (dec_ret != IMX_VPU_DEC_RETURN_CODE_OK)
        fprintf(stderr, "could not decode this JPEG image : %s\n", imx_vpu_dec_error_string(dec_ret));
    /* Input data is not needed anymore, so free the input buffer */
    /* Get some information about the the frame
     * Note that the info is only available *after* calling imx_vpu_jpeg_dec_decode() */
    imx_vpu_jpeg_dec_get_info(jpegContex->jpeg_decoder, &info);
        "aligned frame size: %u x %u pixel  actual frame size: %u x %u pixel  Y/Cb/Cr stride: %u/%u/%u  Y/Cb/Cr size: %u/%u/%u  Y/Cb/Cr offset: %u/%u/%u  color format: %s\n",
        info.aligned_frame_width, info.aligned_frame_height,
        info.actual_frame_width, info.actual_frame_height,
        info.y_stride, info.cbcr_stride, info.cbcr_stride,
        info.y_size, info.cbcr_size, info.cbcr_size,
        info.y_offset, info.cb_offset, info.cr_offset,
    if (info.framebuffer == NULL)
        fprintf(stderr, "could not decode this JPEG image : no framebuffer returned\n");
    FILE* shm_fd = fopen("/dev/shm/tmp.raw", "wb");
    /* Map the DMA buffer of the decoded picture, write out the decoded pixels, and unmap the buffer again */
    num_out_byte = info.y_size + info.cbcr_size * 2;
    fprintf(stderr, "decoded output picture:  writing %u byte\n", num_out_byte);
    mapped_virtual_address = imx_vpu_dma_buffer_map(info.framebuffer->dma_buffer, IMX_VPU_MAPPING_FLAG_READ);
    fwrite(mapped_virtual_address, 1, num_out_byte, shm_fd);
    /* Decoded frame is no longer needed, so inform the decoder that it can reclaim it */
    imx_vpu_jpeg_dec_frame_finished(jpegContex->jpeg_decoder, info.framebuffer);
    { // color space conversion
        int file_fd;
        FILE* file_out;
        file_fd = open("/dev/shm/tmp.raw", O_RDWR, 0);
        printf("color space conversion init\n");
        int file_size = lseek(file_fd, 0, SEEK_END);
        printf("post lseek, file_size:%i\n", file_size);
        void * raw_image = mmap(0, file_size, PROT_READ, MAP_SHARED, file_fd, 0);
        printf("post mmap\n");
        ipu_csc_t csc;
        ipu_csc_format_t input_format = { info.aligned_frame_width, info.aligned_frame_height, 16, V4L2_PIX_FMT_YUV422P };
        // ipu_csc_format_t output_format = { info.aligned_frame_width, info.aligned_frame_height, 16, V4L2_PIX_FMT_YUV420 };
        ipu_csc_format_t output_format = { info.aligned_frame_width, info.aligned_frame_height, 12, V4L2_PIX_FMT_YUV420 };
        if (ipu_csc_init(&csc, &input_format, &output_format) < 0) {
            perror("ipu csc init failed");
        printf("post ipu_csc_init\n");
        // Output buffer
        printf("output_image size: %i\n", info.aligned_frame_width * info.aligned_frame_height * output_format.bpp / 8);
        unsigned char output_image[ info.aligned_frame_width * info.aligned_frame_height * output_format.bpp / 8 ];
        memset(output_image, 0, sizeof(output_image));
        printf("post memset\n");
        if (ipu_csc_convert(&csc, raw_image, output_image) < 0) {
        } else {
            printf("Conversion done.\n");
        file_out = fopen("/dev/shm/tmp_conv.raw", "wb");
        fwrite(output_image, sizeof(output_image), 1, file_out);
        printf("color conversion end\n");
    } // color space conversion end
    /* Init h264 encoder */
    memset(&open_params, 0, sizeof(open_params));
    imx_vpu_enc_set_default_open_params(IMX_VPU_CODEC_FORMAT_H264, &open_params);
    open_params.bitrate = 0;
    open_params.frame_width = info.aligned_frame_width;
    open_params.frame_height = info.aligned_frame_height;
    open_params.frame_rate_numerator = 25;
    open_params.frame_rate_denominator = 1;
    open_params.color_format = IMX_VPU_COLOR_FORMAT_YUV420;
    /* Load the VPU firmware */
    /* Retrieve information about the required bitstream buffer and allocate one based on this */
    imx_vpu_enc_get_bitstream_buffer_info(&(encContex->bitstream_buffer_size), &(encContex->bitstream_buffer_alignment));
    encContex->bitstream_buffer = imx_vpu_dma_buffer_allocate(
    /* Open an encoder instance, using the previously allocated bitstream buffer */
    imx_vpu_enc_open(&(encContex->vpuenc), &open_params, encContex->bitstream_buffer);
    /* Retrieve the initial information to allocate framebuffers for the
     * encoding process (unlike with decoding, these framebuffers are used
     * only internally by the encoder as temporary storage; encoded data
     * doesn't go in there, nor do raw input frames) */
    imx_vpu_enc_get_initial_info(encContex->vpuenc, &(encContex->initial_info));
    encContex->num_framebuffers = encContex->initial_info.min_num_required_framebuffers;
    fprintf(stderr, "num framebuffers: %u\n", encContex->num_framebuffers);
    /* Using the initial information, calculate appropriate framebuffer sizes */
    imx_vpu_calc_framebuffer_sizes(info.color_format, info.actual_frame_width, info.actual_frame_height, encContex->initial_info.framebuffer_alignment, 0, 0, &(encContex->calculated_sizes));
        "calculated sizes:  frame width&height: %dx%d  Y stride: %u  CbCr stride: %u  Y size: %u  CbCr size: %u  MvCol size: %u  total size: %u\n",
        encContex->calculated_sizes.aligned_frame_width, encContex->calculated_sizes.aligned_frame_height,
        encContex->calculated_sizes.y_stride, encContex->calculated_sizes.cbcr_stride,
        encContex->calculated_sizes.y_size, encContex->calculated_sizes.cbcr_size, encContex->calculated_sizes.mvcol_size,
    /* Allocate memory blocks for the framebuffer and DMA buffer structures,
     * and allocate the DMA buffers themselves */
    encContex->framebuffers = malloc(sizeof(ImxVpuFramebuffer) * encContex->num_framebuffers);
    encContex->fb_dmabuffers = malloc(sizeof(ImxVpuDMABuffer*) * encContex->num_framebuffers);
    for (unsigned int i = 0; i < encContex->num_framebuffers; ++i)
        /* Allocate a DMA buffer for each framebuffer. It is possible to specify alternate allocators;
         * all that is required is that the allocator provides physically contiguous memory
         * (necessary for DMA transfers) and respecs the alignment value. */
        encContex->fb_dmabuffers[i] = imx_vpu_dma_buffer_allocate(imx_vpu_dec_get_default_allocator(), encContex->calculated_sizes.total_size, encContex->initial_info.framebuffer_alignment, 0);
        imx_vpu_fill_framebuffer_params(&(encContex->framebuffers[i]), &(encContex->calculated_sizes), encContex->fb_dmabuffers[i], 0);
    /* allocate DMA buffers for the raw input frames. Since the encoder can only read
     * raw input pixels from a DMA memory region, it is necessary to allocate one,
     * and later copy the pixels into it. In production, it is generally a better
     * idea to make sure that the raw input frames are already placed in DMA memory
     * (either allocated by imx_vpu_dma_buffer_allocate() or by some other means of
     * getting DMA / physically contiguous memory with known physical addresses). */
    encContex->input_fb_dmabuffer = imx_vpu_dma_buffer_allocate(imx_vpu_dec_get_default_allocator(), encContex->calculated_sizes.total_size, encContex->initial_info.framebuffer_alignment, 0);
    imx_vpu_fill_framebuffer_params(&(encContex->input_framebuffer), &(encContex->calculated_sizes), encContex->input_fb_dmabuffer, 0);
    /* Actual registration is done here. From this moment on, the VPU knows which buffers to use for
     * storing temporary frames into. This call must not be done again until encoding is shut down. */
    imx_vpu_enc_register_framebuffers(encContex->vpuenc, encContex->framebuffers, encContex->num_framebuffers);
    /* Set up the input frame. The only field that needs to be
     * set is the input framebuffer. The encoder will read from it.
     * The rest can remain zero/NULL. */
    memset(&input_frame, 0, sizeof(input_frame));
    // input_frame.framebuffer = info.framebuffer;
    input_frame.framebuffer = &(encContex->input_framebuffer);
    /* Set the encoding parameters for this frame. quant_param 0 is
     * the highest quality in h.264 constant quality encoding mode.
     * (The range in h.264 is 0-51, where 0 is best quality and worst
     * compression, and 51 vice versa.) */
    memset(&enc_params, 0, sizeof(enc_params));
    enc_params.quant_param = 0;
    enc_params.acquire_output_buffer = acquire_output_buffer;
    enc_params.finish_output_buffer = finish_output_buffer;
    enc_params.output_buffer_context = NULL;
    /* Set up the output frame. Simply setting all fields to zero/NULL
     * is enough. The encoder will fill in data. */
    memset(&output_frame, 0, sizeof(output_frame));
    for (int nframe = 0; nframe < 100; nframe++)
        uint8_t *mapped_virtual_address;
        void *output_block;
        FILE* raw_file;
        raw_file = fopen("/dev/shm/tmp_conv.raw", "rb");
        /* Read uncompressed pixels into the input DMA buffer */
        mapped_virtual_address = imx_vpu_dma_buffer_map(encContex->input_fb_dmabuffer, IMX_VPU_MAPPING_FLAG_WRITE);
        fread(mapped_virtual_address, 1, num_out_byte, raw_file);
        /* The actual encoding */
        imx_vpu_enc_encode(encContex->vpuenc, &input_frame, &output_frame, &enc_params, &output_code);
        /* Write out the encoded frame to the output file. The encoder
         * will have called acquire_output_buffer(), which acquires a
         * buffer by malloc'ing it. The "handle" in this example is
         * just the pointer to the allocated memory. This means that
         * here, acquired_handle is the pointer to the encoded frame
         * data. Write it to file, and then free the previously
         * allocated block. In production, the acquire function could
         * retrieve an output memory block from a buffer pool for
         * example. */
        output_block = output_frame.acquired_handle;
        fwrite(output_block, 1, output_frame.data_size, encContex->fout);
    /* Close the previously opened encoder instance */
    /* Free all allocated memory (both regular and DMA memory) */
    for (unsigned int i = 0; i < encContex->num_framebuffers; ++i)
    /* Unload the VPU firmware */
    /* Shut down the JPEG decoder */

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