1 files changed, 105 insertions, 0 deletions
diff --git a/src/outputBuffer_xfade.h b/src/outputBuffer_xfade.h
new file mode 100644
index 000000000..0f3a4d5a7
--- /dev/null
+++ b/src/outputBuffer_xfade.h
@@ -0,0 +1,105 @@
+#ifndef OUTPUT_BUFFER_XFADE_H
+#define OUTPUT_BUFFER_XFADE_H
+
+#include "os_compat.h"
+#include "audio.h"
+#include "pcm_utils.h"
+
+static struct ob_chunk *get_chunk(struct iovec vec[2], size_t i);
+static size_t calculate_xfade_chunks(struct iovec vec[2])
+{
+	size_t chunks;
+	struct ob_chunk *c;
+	size_t nr;
+	AudioFormat *af = &ob.audio_format;
+
+	assert(pthread_equal(ob.thread, pthread_self()));
+
+	if (!ob.total_time ||
+	    (ob.elapsed_time + ob.xfade_time) < ob.total_time ||
+	    !isCurrentAudioFormat(af))
+		return ob.nr_bpp; /* too early, don't enable xfade yet */
+
+	assert(af->bits > 0);
+	assert(af->channels > 0);
+	assert(af->sampleRate > 0);
+
+	chunks = af->sampleRate * af->bits * af->channels / 8.0 / CHUNK_SIZE;
+	chunks = chunks * (ob.xfade_time + 0.5);
+
+	assert(ob.index->size >= ob.nr_bpp);
+	if (chunks > (ob.index->size - ob.nr_bpp))
+		chunks = ob.index->size - ob.nr_bpp;
+	DEBUG("calculated xfade chunks: %d\n", chunks);
+	nr = vec[0].iov_len + vec[1].iov_len;
+
+	if (chunks > nr)
+		return chunks; /* not enough work with */
+
+	c = get_chunk(vec, chunks);
+	assert(c);
+	if (c->seq == ob.seq_player) {
+		do {
+			if (!(c = get_chunk(vec, ++chunks)))
+				return chunks; /* not enough to work with */
+		} while (c->seq == ob.seq_player);
+	} else {
+		do {
+			c = get_chunk(vec, --chunks);
+			assert(c);
+		} while (c->seq == ob.seq_decoder);
+		assert((c = get_chunk(vec, chunks)));
+		assert(c->seq != ob.seq_decoder);
+		++chunks;
+		assert((c = get_chunk(vec, chunks)));
+		assert(c->seq == ob.seq_decoder);
+	}
+	DEBUG("adjusted xfade chunks: %d\n", chunks);
+
+	ob.xfade_cur = chunks;
+	ob.xfade_max = chunks;
+	assert(ob.xfade_state == XFADE_DISABLED);
+	ob.xfade_state = XFADE_ENABLED;
+	return chunks;
+}
+
+static size_t xfade_chunks_needed(struct iovec vec[2])
+{
+	assert(pthread_equal(ob.thread, pthread_self()));
+
+	if (ob.xfade_state == XFADE_DISABLED)
+		return calculate_xfade_chunks(vec);
+	assert(ob.xfade_state == XFADE_ENABLED);
+	return ob.xfade_max;
+}
+
+static void xfade_mix(struct ob_chunk *a, struct ob_chunk *b)
+{
+	assert(pthread_equal(ob.thread, pthread_self()));
+	assert(ob.xfade_state == XFADE_ENABLED);
+	assert(ob.xfade_cur <= ob.xfade_max);
+	assert(b);
+	assert(a != b);
+	assert(a->len <= CHUNK_SIZE);
+	assert(b->len <= CHUNK_SIZE);
+	if (b->seq == a->seq) {
+		/* deal with small rounding errors */
+		DEBUG("seq_match: %d == %d\n", a->seq, b->seq);
+		return;
+	}
+
+	/* as xfade_cur increases, b is scaled more and a is scaled less */
+	pcm_mix(a->data, b->data, a->len, b->len,
+	        &ob.audio_format, ((float)ob.xfade_cur) / ob.xfade_max);
+
+	/* next time we fade more until we have nothing to fade */
+	if (ob.xfade_cur)
+		--ob.xfade_cur;
+	if (b->len > a->len) {
+		DEBUG("reassign len: %d => %d\n", a->len, b->len);
+		a->len = b->len;
+	}
+	b->len = 0; /* invalidate the chunk we already mixed in */
+}
+
+#endif /* OUTPUT_BUFFER_XFADE_H */