Support other sample rates than 48 kHz.

[bmusb] / bmusb.cpp

diff --git a/bmusb.cpp b/bmusb.cpp
index 088fc9853f5d6a3df87ab00ac44971b768200f64..663a235f05a75698283d6dd5f5ea59295c2f0db3 100644 (file)
--- a/bmusb.cpp
+++ b/bmusb.cpp
@@ -1,4 +1,4 @@
-// Intensity Shuttle USB3 capture driver, v0.5.4
+// Intensity Shuttle USB3 capture driver, v0.6.0
 // Can download 8-bit and 10-bit UYVY/v210-ish frames from HDMI, quite stable
 // (can do captures for hours at a time with no drops), except during startup
 // 576p60/720p60/1080i60 works, 1080p60 does not work (firmware limitation)
@@ -241,6 +241,26 @@ bool decode_video_format(uint16_t video_format, VideoFormat *decoded_video_forma
        return false;
 }
 
+// There are seemingly no direct indicators of sample rate; you just get
+// one frame's worth and have to guess from that.
+int guess_sample_rate(const VideoFormat &video_format, size_t len)
+{
+       size_t num_samples = len / 3 / 8;
+       size_t num_samples_per_second = num_samples * video_format.frame_rate_nom / video_format.frame_rate_den;
+
+       // See if we match or are very close to any of the mandatory HDMI sample rates.
+       const int candidate_sample_rates[] = { 32000, 44100, 48000 };
+       for (int rate : candidate_sample_rates) {
+               if (abs(int(num_samples_per_second) - rate) < 50) {
+                       return rate;
+               }
+       }
+
+       fprintf(stderr, "%ld samples at %d/%d fps (%ld Hz) matches no known sample rate, assuming 48000 Hz\n",
+               num_samples, video_format.frame_rate_nom, video_format.frame_rate_den, num_samples_per_second);
+       return 48000;
+}
+
 }  // namespace
 
 FrameAllocator::~FrameAllocator() {}
@@ -332,6 +352,7 @@ void BMUSBCapture::dequeue_thread_func()
        if (has_dequeue_callbacks) {
                dequeue_init_callback();
        }
+       size_t last_sample_rate = 48000;
        while (!dequeue_thread_should_quit) {
                unique_lock<mutex> lock(queue_lock);
                queues_not_empty.wait(lock, [this]{ return dequeue_thread_should_quit || (!pending_video_frames.empty() && !pending_audio_frames.empty()); });
@@ -343,6 +364,7 @@ void BMUSBCapture::dequeue_thread_func()
                AudioFormat audio_format;
                audio_format.bits_per_sample = 24;
                audio_format.num_channels = 8;
+               audio_format.sample_rate = last_sample_rate;
                if (uint16_less_than_with_wraparound(video_timecode, audio_timecode)) {
                        printf("Video block 0x%04x without corresponding audio block, dropping.\n",
                                video_timecode);
@@ -383,10 +405,15 @@ void BMUSBCapture::dequeue_thread_func()
                        VideoFormat video_format;
                        audio_format.id = audio_frame.format;
                        if (decode_video_format(video_frame.format, &video_format)) {
+                               if (audio_frame.frame.len != 0) {
+                                       audio_format.sample_rate = guess_sample_rate(video_format, audio_frame.frame.len);
+                                       last_sample_rate = audio_format.sample_rate;
+                               }
                                frame_callback(video_timecode,
                                               video_frame.frame, HEADER_SIZE, video_format,
                                               audio_frame.frame, AUDIO_HEADER_SIZE, audio_format);
                        } else {
+                               audio_format.sample_rate = last_sample_rate;
                                frame_callback(video_timecode,
                                               FrameAllocator::Frame(), 0, video_format,
                                               audio_frame.frame, AUDIO_HEADER_SIZE, audio_format);
@@ -453,8 +480,8 @@ void BMUSBCapture::start_new_audio_block(const uint8_t *start)
                //dump_audio_block();
                queue_frame(format, timecode, current_audio_frame, &pending_audio_frames);
        }
-       //printf("Found audio block start, format 0x%04x timecode 0x%04x, previous block length was %d\n",
-       //      format, timecode, read_current_audio_block);
+       //printf("Found audio block start, format 0x%04x timecode 0x%04x\n",
+       //      format, timecode);
        current_audio_frame = audio_frame_allocator->alloc_frame();
 }