[FFmpeg-devel] [PATCH] decklink: support all valid numbers of audio channels

[Matthias Hunstock]

As it is already written in the documentation, BMD DeckLink cards
are capable of capturing 2, 8 or 16 audio channels (for SDI Inputs).
Currently the value is hardcoded to 2. Introduces new option.

Signed-off-by: Matthias Hunstock <atze at fem.tu-ilmenau.de>
---
 doc/indevs.texi                 | 13 ++++++++++++-
 libavdevice/decklink_common_c.h |  1 +
 libavdevice/decklink_dec.cpp    | 16 ++++++++++++++--
 libavdevice/decklink_dec_c.c    |  2 ++
 4 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/doc/indevs.texi b/doc/indevs.texi
index 6cf626d..6003b9f 100644
--- a/doc/indevs.texi
+++ b/doc/indevs.texi
@@ -218,7 +218,8 @@ On Windows, you need to run the IDL files through @command{widl}.
 DeckLink is very picky about the formats it supports. Pixel format is
 uyvy422 or v210, framerate and video size must be determined for your device with
 @command{-list_formats 1}. Audio sample rate is always 48 kHz and the number
-of channels can be 2, 8 or 16.
+of channels can be 2, 8 or 16. Note that all audio channels are bundled in one single
+audio track.
 
 @subsection Options
 
@@ -236,6 +237,10 @@ Defaults to @option{false}.
 If set to @samp{1}, video is captured in 10 bit v210 instead
 of uyvy422. Not all Blackmagic devices support this option.
 
+ at item audio_channels
+Defines number of audio channels to capture. Must be @samp{2}, @samp{8} or @samp{16}.
+Defaults to @samp{2}.
+
 @end table
 
 @subsection Examples
@@ -266,6 +271,12 @@ Capture video clip at 1080i50 10 bit:
 ffmpeg -bm_v210 1 -f decklink -i 'UltraStudio Mini Recorder@@11' -acodec copy -vcodec copy output.avi
 @end example
 
+ at item
+Capture video clip at 1080i50 with 16 audio channels:
+ at example
+ffmpeg -audio_channels 16 -f decklink -i 'UltraStudio Mini Recorder@@11' -acodec copy -vcodec copy output.avi
+ at end example
+
 @end itemize
 
 @section dshow
diff --git a/libavdevice/decklink_common_c.h b/libavdevice/decklink_common_c.h
index fb2b788..403956f 100644
--- a/libavdevice/decklink_common_c.h
+++ b/libavdevice/decklink_common_c.h
@@ -29,5 +29,6 @@ struct decklink_cctx {
     int list_formats;
     double preroll;
     int v210;
+    int audio_channels;
 };
 
diff --git a/libavdevice/decklink_dec.cpp b/libavdevice/decklink_dec.cpp
index 89f93de..1588933 100644
--- a/libavdevice/decklink_dec.cpp
+++ b/libavdevice/decklink_dec.cpp
@@ -381,6 +381,17 @@ av_cold int ff_decklink_read_header(AVFormatContext *avctx)
     ctx->preroll      = cctx->preroll;
     cctx->ctx = ctx;
 
+    /* Check audio channel option for valid values: 2, 8 or 16 */
+    switch (cctx->audio_channels) {
+        case 2:
+        case 8:
+        case 16:
+            break;
+        default:
+            av_log(avctx, AV_LOG_ERROR, "Value of channels option must be one of 2, 8 or 16\n");
+            return AVERROR(EINVAL);
+    }
+
     iter = CreateDeckLinkIteratorInstance();
     if (!iter) {
         av_log(avctx, AV_LOG_ERROR, "Could not create DeckLink iterator\n");
@@ -458,7 +469,7 @@ av_cold int ff_decklink_read_header(AVFormatContext *avctx)
     st->codec->codec_type  = AVMEDIA_TYPE_AUDIO;
     st->codec->codec_id    = AV_CODEC_ID_PCM_S16LE;
     st->codec->sample_rate = bmdAudioSampleRate48kHz;
-    st->codec->channels    = 2;
+    st->codec->channels    = cctx->audio_channels;
     avpriv_set_pts_info(st, 64, 1, 1000000);  /* 64 bits pts in us */
     ctx->audio_st=st;
 
@@ -488,7 +499,8 @@ av_cold int ff_decklink_read_header(AVFormatContext *avctx)
 
     ctx->video_st=st;
 
-    result = ctx->dli->EnableAudioInput(bmdAudioSampleRate48kHz, bmdAudioSampleType16bitInteger, 2);
+    av_log(avctx, AV_LOG_VERBOSE, "Using %d input audio channels\n", ctx->audio_st->codec->channels);
+    result = ctx->dli->EnableAudioInput(bmdAudioSampleRate48kHz, bmdAudioSampleType16bitInteger, ctx->audio_st->codec->channels);
 
     if (result != S_OK) {
         av_log(avctx, AV_LOG_ERROR, "Cannot enable audio input\n");
diff --git a/libavdevice/decklink_dec_c.c b/libavdevice/decklink_dec_c.c
index b1a65e6..487bfd6 100644
--- a/libavdevice/decklink_dec_c.c
+++ b/libavdevice/decklink_dec_c.c
@@ -32,6 +32,8 @@ static const AVOption options[] = {
     { "list_devices", "list available devices"  , OFFSET(list_devices), AV_OPT_TYPE_INT   , { .i64 = 0   }, 0, 1, DEC },
     { "list_formats", "list supported formats"  , OFFSET(list_formats), AV_OPT_TYPE_INT   , { .i64 = 0   }, 0, 1, DEC },
     { "bm_v210",      "v210 10 bit per channel" , OFFSET(v210),         AV_OPT_TYPE_INT   , { .i64 = 0   }, 0, 1, DEC },
+    { "audio_channels", "number of audio channels; must be 2, 8 or 16",
+                                                  OFFSET(audio_channels), AV_OPT_TYPE_INT,  { .i64 = 2   }, 2, 16, DEC },
     { NULL },
 };
 
-- 
2.4.10