RAW audio capture from HDMI using DeckLink Mini Recorder 4K
devil coder
mdamirraza at gmail.com
Thu Mar 12 13:04:32 UTC 2020
Hi Experts,
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 software's.
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;
}
/
-----
adi
--
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