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• HTML5 Media and Accessibility presentation

  23 février 2010, par silvia

  Today, I was invited to give a talk at my old workplace CSIRO about the HTML5 media elements and accessibility. A lot of the things that have gone into Ogg and that are now being worked on in the W3C in different working groups – including the Media Fragments and HTML5 WGs – were also (...)

• Seeking while Transcoding videos from Windows Media Player

  3 juillet 2015, par prakharsingh95

  I am using Windows Media Player’s default DLNA server and the streaming is great.

  However, when I try to stream AC3 to VLC for iOS, on iPad Air 2, it converts it to a large number of available formats :
  

  If I try AVC_MP4_BL_L31_HD_AAC, this provides the untranscoded media, which I can stream and SEEK. However, AC3 is not playable.

  However, AVC_MP4_MP_HD_720p_AAC is transcoded by Windows Media Player on the fly, but is NOT SEEKABLE.

  How do I add support for seeking transcoded media from Windows Media Player ?

  I can convert using ffmpeg, but I would prefer the above solution.

• RAW audio capture from HDMI using DeckLink Mini Recorder 4K

  12 mars 2020, par Amir Raza

  I need to capture audio from TI DSP hardware/Laptop. So I opted "DeckLink Mini Recorder 4K Audio" and it connected to desktop.
  By using Decklink API’s I am able to capture audio (PCM) with 32-bit depth. But when I used media express to capture, and extracted audio
  using FFmpeg and I am getting audio (PCM) with 24-bit depth.

  Question
  1) Does this device "DeckLink Mini Recorder 4K Audio" converts audio from 32-bit to 24-bit ?
  2) Is this device "DeckLink Mini Recorder 4K Audio" bit-exact/loss-less ?

  consider the below test scenario.

  I am playing audio(PCM) by MPC-HC/VLC/Groove player in laptop and capture audio(PCM) using "DeckLink Mini Recorder 4K Audio"
  connected to desktop, The capture audio is bit-exact with the streamed input.?

  i.e ffmpeg.exe -i HDMI_Output1.av1 -vn -c:a copy out.wav

  Note :
  i am using Blackmagic_Desktop_Video_Windows_11.5 & Blackmagic_DeckLink_SDK_11.5 softwares.

  I have added the Decklink API code snippet.

  void main()
  
  {
  
    IDeckLinkIterator* deckLinkIterator = NULL;
  
    IDeckLinkAttributes* deckLinkAttributes = NULL;
  
    IDeckLink* deckLink = NULL;
  
    IDeckLinkInput* deckLinkInput = NULL;
  
    NotificationCallback* notificationCallback = NULL;
  
    HRESULT result;
  
    BOOL supported;
  
    int returnCode = 1;
  
  #ifdef WRITE_WAV_FILE
  
    wave_header wh;
  
    unsigned octet_depth;
  
  #endif
  
    Initialize();
  
  #ifdef _WIN32
  
    MutexHandle = CreateMutex(NULL, /* security attributes */
  
                              FALSE, /* initially not owned */
  
                              NULL); /* Name */
  
  #endif
  
    /* Create an IDeckLinkIterator object to enumerate all DeckLink cards in the system */
  
    if (GetDeckLinkIterator(&deckLinkIterator) != S_OK)
  
    {
  
      fprintf(stderr, "A DeckLink iterator could not be created.  The DeckLink drivers may not be installed.\n");
  
      goto bail;
  
    }
  
    /* Obtain the first DeckLink device */
  
    result = deckLinkIterator->Next(&deckLink);
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not find DeckLink device - result = %08x\n", result);
  
      goto bail;
  
    }
  
  
  
    /* Obtain the Attributes interface for the DeckLink device */
  
    result = deckLink->QueryInterface(IID_IDeckLinkAttributes, (void**)&deckLinkAttributes);
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not obtain the IDeckLinkAttributes interface - result = %08x\n", result);
  
      goto bail;
  
    }
  
  
  
    /* Determine whether the DeckLink device supports input format detection */
  
    result = deckLinkAttributes->GetFlag(BMDDeckLinkSupportsInputFormatDetection, &supported);
  
    if ((result != S_OK) || (supported == false))
  
    {
  
      fprintf(stderr, "Device does not support automatic mode detection\n");
  
      goto bail;
  
    }
  
  
  
    /* Obtain the input interface for the DeckLink device */
  
    result = deckLink->QueryInterface(IID_IDeckLinkInput, (void**)&deckLinkInput);
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not obtain the IDeckLinkInput interface - result = %08x\n", result);
  
      goto bail;
  
    }
  
  
  
    /* Create an instance of notification callback */
  
    notificationCallback = new NotificationCallback(deckLinkInput);
  
    if (notificationCallback == NULL)
  
    {
  
      fprintf(stderr, "Could not create notification callback object\n");
  
      goto bail;
  
    }
  
  
  
    /* Set the callback object to the DeckLink device's input interface */
  
    result = deckLinkInput->SetCallback(notificationCallback);
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not set callback - result = %08x\n", result);
  
      goto bail;
  
    }
  
  
  
    /*  Enable video input with a default video mode and the automatic format detection feature enabled */
  
    result = deckLinkInput->EnableVideoInput(bmdModeHD1080p5994, bmdFormat8BitYUV, bmdVideoInputFlagDefault);
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not enable video input - result = %08x\n", result);
  
      goto bail;
  
    }
  
    nBytesPerSample = (bmdAudioSampleType32bitInteger >> 3);
  
    nChannels = 2;
  
    /*  Enable audio input with a default audio mode and the automatic format detection feature enabled */
  
    result = deckLinkInput->EnableAudioInput(bmdAudioSampleRate48kHz, bmdAudioSampleType32bitInteger, nChannels);
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not enable audio input - result = %08x\n", result);
  
      goto bail;
  
    }
  
  
  
  #ifdef WRITE_WAV_FILE
  
    /* Populate the wave headers */
  
    /* RIFF */
  
    sprintf(&wh.riff.name1[0], "RIFF");
  
    sprintf(&wh.riff.name2[0], "WAVE");
  
    /* format */
  
    octet_depth = (bmdAudioSampleType32bitInteger + 7) / 8;
  
    sprintf(&wh.fmt.name[0], "fmt ");
  
    wh.fmt.size = FMT_SIZE;
  
    wh.fmt.format_type = FMT_TAG_PCM;
  
    wh.fmt.channel_count = (unsigned short)nChannels;
  
    wh.fmt.sample_rate = bmdAudioSampleRate48kHz;
  
    wh.fmt.bits_per_sample = (unsigned short)octet_depth * 8;
  
    wh.fmt.block_alignment = (unsigned short)(octet_depth*nChannels);
  
    wh.fmt.bytes_per_second = (unsigned long)wh.fmt.block_alignment*bmdAudioSampleRate48kHz;
  
    wh.fmt.extra_bytes = (unsigned short)0;
  
    /* data */
  
    sprintf(&wh.data.name[0], "data");
  
  #endif 
  
  
  
    printf("Starting streams\n");
  
  
  
    /* Start capture */
  
    result = deckLinkInput->StartStreams();
  
    if (result != S_OK)
  
    {
  
      fprintf(stderr, "Could not start capture - result = %08x\n", result);
  
      goto bail;
  
    }
  
  #ifdef WRITE_WAV_FILE
  
    FILE *fp = fopen("HDMI_Output.wav", "wb");
  
  #else
  
    FILE *fp = fopen("HDMI_Output.bin","wb");
  
  #endif
  
    char *ptrCopy;
  
    float *fPtr;
  
    unsigned int zeroCntr, trailingZerosCnt;
  
    do
  
    {
  
        zeroCntr = 0;
  
        trailingZerosCnt = 0;
  
  #ifdef _WIN32
  
        WaitForSingleObject(MutexHandle, /* handle */
  
                            INFINITE); /* time-out interval */
  
  #endif
  
        int bytesInQueue = (int)((long long)aBufPtr - (long long)aBufWritePtr);
  
        ptrCopy = (char *)aBufPtr;
  
  #ifdef _WIN32
  
        ReleaseMutex(MutexHandle);
  
  #endif
  
        if (bytesInQueue > 0)
  
        {
  
  #ifdef STRIP_ZEROS
  
            /* Parse data for zeros */
  
            fPtr = (float *)aBufWritePtr;
  
            for (int i = 0; i < (bytesInQueue >> 2); i++)
  
            {
  
                if (*(fPtr + i) == 0.0)
  
                    zeroCntr++;
  
                else
  
                    break;
  
            }
  
            aBufWritePtr += (zeroCntr << 2);
  
            bytesInQueue -= (zeroCntr << 2);
  
  #endif
  
            if (bytesInQueue > 0)
  
            {
  
                fPtr = (float *)aBufWritePtr;
  
                for (int i = 0; i < (bytesInQueue >> 2); i++)
  
                {
  
                    fwrite(fPtr, 4, 1, fp);
  
                    fflush(fp);
  
  
  
                    if (*fPtr == 0.0)
  
                        trailingZerosCnt++;
  
                    else
  
                        trailingZerosCnt = 0;
  
  
  
                    if (trailingZerosCnt >= NUM_TRAIL_ZEROS_TRESHOLD)
  
                        break;
  
  
  
                    fPtr++;
  
                }
  
            }
  
        }
  
        aBufWritePtr = ptrCopy;
  
        Sleep(100);
  
    } while (trailingZerosCnt < NUM_TRAIL_ZEROS_TRESHOLD);
  
  
  
    fclose (fp);
  
  #ifdef STRIP_ZEROS
  
    /* Remove trailing zeros, write wave header */
  
  #ifdef WRITE_WAV_FILE
  
    fp = fopen("HDMI_Output.wav", "rb");
  
  #else
  
    fp = fopen("HDMI_Output.bin", "rb");
  
  #endif
  
    fseek(fp, 0, SEEK_END);
  
    int size = ftell(fp);
  
    size = size - (NUM_TRAIL_ZEROS_TRESHOLD << 2);
  
    printf(" \n size of hearder = %d", size);
  
  #ifdef WRITE_WAV_FILE
  
    wh.data.size = size;
  
    wh.riff.size = wh.data.size + sizeof(wave_format) + sizeof(wave_RIFF);
  
    printf(" \n size of hearderwh.riff.size = %d", wh.riff.size);
  
  #endif
  
    char * tmpBuf = (char *)malloc(size);
  
    fseek(fp, 0, SEEK_SET);
  
    fread(tmpBuf, 1, size, fp);
  
    fclose(fp);
  
  #endif
  
  #ifdef WRITE_WAV_FILE
  
    fp = fopen("HDMI_Output.wav", "wb");
  
    /* write the wave header */
  
    fwrite(&wh, 1, sizeof(wave_header), fp);
  
    /* Write the zero stripped PCM data */
  
    fwrite(tmpBuf, 1, size, fp);
  
    free(tmpBuf);
  
    fflush(fp);
  
    fclose(fp);
  
  #endif
  
  bail:
  
    /* Stop capture */
  
    result = deckLinkInput->StopStreams();
  
  
  
    /* Disable the video input interface */
  
    result = deckLinkInput->DisableVideoInput();
  
  
  
    /* return success */
  
    returnCode = 0;
  
  
  
    /* Release resources */
  
  
  
    /* Release the attributes interface */
  
    if (deckLinkAttributes != NULL)
  
      deckLinkAttributes->Release();
  
  
  
    /* Release the video input interface */
  
    if (deckLinkInput != NULL)
  
      deckLinkInput->Release();
  
  
  
    /* Release the Decklink object */
  
    if (deckLink != NULL)
  
      deckLink->Release();
  
  
  
    /* Release the DeckLink iterator */
  
    if (deckLinkIterator != NULL)
  
      deckLinkIterator->Release();
  
  
  
    /* Release the notification callback object */
  
    if (notificationCallback)
  
      delete notificationCallback;
  
  }