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• 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;
  
  }

• libavformat/mpegts : expose raw packet size

  31 janvier 2014, par Leandro Dorileo

  libavformat/mpegts : expose raw packet size
  We cannot easily determine if an mpeg TS’s packet size is DVHS, FEC
  
  or so on, for that we need to expose the internal raw_packet_size
  
  field.
  Signed-off-by : Anton Khirnov <anton@khirnov.net>
  

  • [DBH] libavformat/mpegts.c

• Accurate FFmpeg capture start time

  28 juillet 2016, par Adam

  I’m using ffmpeg from the command line to capture from a webcam to a file using the following :

  ffmpeg -y -rtbufsize 702000k -f dshow -s 320x240 -r 25 -i video="<device>" -t 10 -vcodec mjpeg -q:v 2 out.mp4
  
  </device>

  There is a slight delay between executing the command and the start of the capture ( 0.5 sec).
  I’m trying to find a way to accurately determine the start time (UTC/GMT) of the capture.

  My initial thought was to use the file-creation time as this might accurately reflect when the first frame was encoded (as opposed to when the command was executed). Unfortunately the file creation time is only accurate to the second which is not precise enough (and I’m not sure this would have given an accurate result anyway).

  My next thought was to use ffmpegs timestamp option. According to the documentation (http://www.ffmpeg.org/ffmpeg.html) :

  ‘-timestamp time (output)’

  Set the recording timestamp in the container. The syntax for time is:
  
  
  
  now|([(YYYY-MM-DD|YYYYMMDD)[T|t| ]]((HH:MM:SS[.m...])|(HHMMSS[.m...]))[Z|z])

  If the value is "now" it takes the current time. Time is local time unless ’Z’ or
  ’z’ is appended, in which case it is interpreted as UTC. If the year-month-day part
  is not specified it takes the current year-month-day.

  So I added the option :

  ffmpeg -y -rtbufsize 702000k -f dshow -s 320x240 -r 25 -i video="<device>" -t 10 -vcodec mjpeg -q:v 2 -timestamp now out.mp4
  
  </device>

  Unfortunately ffmpeg doesn’t seem to like this :

  Option timestamp (set the recording timestamp (’now’ to set the
  current time)) cannot be applied to output file out.mp4 — you are
  trying to apply an input option to an output file or vice versa. Move
  this option before the file it belongs to.

  Error parsing options for output file out.mp4.

  Error opening output files : Error number -22 occurred

  The documentation says -timestamp is an output option and it appears to be applied to the output file so I’m confused by this error.

  Can anyone suggest a way to accurately determine the capture start time ?

  Does anyone know why the -timestamp option gives an error ?