diff options
| -rw-r--r-- | doc/indevs.texi | 9 | ||||
| -rw-r--r-- | libavdevice/dshow.c | 51 |
2 files changed, 60 insertions, 0 deletions
diff --git a/doc/indevs.texi b/doc/indevs.texi index 86f10a3..264dc58 100644 --- a/doc/indevs.texi +++ b/doc/indevs.texi @@ -112,6 +112,15 @@ defaults to 0). Set audio device number for devices with same name (starts at 0, defaults to 0). +@item audio_buffer_size +Set audio device buffer size in milliseconds (which can directly +impact latency, depending on the device). +Defaults to using the audio device's +default buffer size (typically some multiple of 500ms). +Setting this value too low can degrade performance. +See also +@url{http://msdn.microsoft.com/en-us/library/windows/desktop/dd377582(v=vs.85).aspx} + @end table @subsection Examples diff --git a/libavdevice/dshow.c b/libavdevice/dshow.c index ea6c21c..18adf8f 100644 --- a/libavdevice/dshow.c +++ b/libavdevice/dshow.c @@ -36,6 +36,7 @@ struct dshow_ctx { int list_options; int list_devices; + int audio_buffer_size; IBaseFilter *device_filter[2]; IPin *device_pin[2]; @@ -447,6 +448,51 @@ end: } /** + * Set audio device buffer size in milliseconds (which can directly impact + * latency, depending on the device). + */ +static int +dshow_set_audio_buffer_size(AVFormatContext *avctx, IPin *pin) +{ + struct dshow_ctx *ctx = avctx->priv_data; + IAMBufferNegotiation *buffer_negotiation = NULL; + ALLOCATOR_PROPERTIES props = { -1, -1, -1, -1 }; + IAMStreamConfig *config = NULL; + AM_MEDIA_TYPE *type = NULL; + int ret = AVERROR(EIO); + + if (IPin_QueryInterface(pin, &IID_IAMStreamConfig, (void **) &config) != S_OK) + goto end; + if (IAMStreamConfig_GetFormat(config, &type) != S_OK) + goto end; + if (!IsEqualGUID(&type->formattype, &FORMAT_WaveFormatEx)) + goto end; + + props.cbBuffer = (((WAVEFORMATEX *) type->pbFormat)->nAvgBytesPerSec) + * ctx->audio_buffer_size / 1000; + + if (IPin_QueryInterface(pin, &IID_IAMBufferNegotiation, (void **) &buffer_negotiation) != S_OK) + goto end; + if (IAMBufferNegotiation_SuggestAllocatorProperties(buffer_negotiation, &props) != S_OK) + goto end; + + ret = 0; + +end: + if (buffer_negotiation) + IAMBufferNegotiation_Release(buffer_negotiation); + if (type) { + if (type->pbFormat) + CoTaskMemFree(type->pbFormat); + CoTaskMemFree(type); + } + if (config) + IAMStreamConfig_Release(config); + + return ret; +} + +/** * Cycle through available pins using the device_filter device, of type * devtype, retrieve the first output pin and return the pointer to the * object found in *ppin. @@ -513,6 +559,10 @@ dshow_cycle_pins(AVFormatContext *avctx, enum dshowDeviceType devtype, goto next; } } + if (devtype == AudioDevice && ctx->audio_buffer_size) { + if (dshow_set_audio_buffer_size(avctx, pin) < 0) + goto next; + } if (IPin_EnumMediaTypes(pin, &types) != S_OK) goto next; @@ -952,6 +1002,7 @@ static const AVOption options[] = { { "false", "", 0, AV_OPT_TYPE_CONST, {.dbl=0}, 0, 0, DEC, "list_options" }, { "video_device_number", "set video device number for devices with same name (starts at 0)", OFFSET(video_device_number), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, DEC }, { "audio_device_number", "set audio device number for devices with same name (starts at 0)", OFFSET(audio_device_number), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, DEC }, + { "audio_buffer_size", "set audio device buffer latency size in milliseconds (default is the device's default)", OFFSET(audio_buffer_size), AV_OPT_TYPE_INT, {.dbl = 0}, 0, INT_MAX, DEC }, { NULL }, }; |
