Add support for partial append window end trimming.

media/base/audio_discard_helper_unittest.cc

Index: media/base/audio_discard_helper_unittest.cc
diff --git a/media/base/audio_discard_helper_unittest.cc b/media/base/audio_discard_helper_unittest.cc
index 1ea0cc6f81657f2d63fcd0f59396448e86c35c65..3156c9a83930c4808808e917811a524be422b9a7 100644
--- a/media/base/audio_discard_helper_unittest.cc
+++ b/media/base/audio_discard_helper_unittest.cc
@@ -329,9 +329,14 @@ TEST(AudioDiscardHelperTest, InitialDiscardAndDiscardPaddingAndDecoderDelay) {
   ASSERT_FALSE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
   ASSERT_TRUE(discard_helper.initialized());
 
-  // Processing another buffer (with the same discard padding) should discard
-  // the back half of the buffer since kDecoderDelay is half a buffer.
+  // Processing another buffer should discard the back half of the buffer since
+  // kDecoderDelay is half a buffer.  The end padding should not be discarded
+  // until another buffer is processed.  kDuration / 4 is chosen for the end
+  // discard since it will force the end discard to start after position zero
+  // within the next decoded buffer.

[acolwell GONE FROM CHROMIUM, 2014/07/24 19:22:14]

I'm confused by this comment. Wasn't the decoder delay handled by the call
above. I thought we didn't get data for the first buffer because the first half
was discarded because of the discard_padding and the second half was discarded
because of the decoding delay.

Since the code below is specifying discarding half of the beginning and one
quarter at the end, shouldn't that mean I should expect a kDuration/4 buffer to
be returned?

I'm really having a hard time visualizing how this test is supposed to be
working.

[DaleCurtis, 2014/07/24 19:58:59]

Decoder delay is forever.  Remember it's not included in the timeline, so all
future buffers must be adjusted to compensate.

[DaleCurtis, 2014/07/29 01:35:09]

Per our offline conversation I've added diagrams explaining exactly what's
happening here.

   encoded_buffer->set_timestamp(kTimestamp + kDuration);
+  encoded_buffer->set_discard_padding(
+      std::make_pair(kDuration / 2, kDuration / 4));
   decoded_buffer = CreateDecodedBuffer(kTestFrames);
   ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
   ASSERT_NEAR(kDecoderDelay * kDataStep,
@@ -344,6 +349,37 @@ TEST(AudioDiscardHelperTest, InitialDiscardAndDiscardPaddingAndDecoderDelay) {
 
   // Verify it was actually the latter half of the buffer that was removed.
   ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
+
+  // Verify the end discard padding is carried over to the next buffer.  Use
+  // kDuration / 2 so that the next buffer has its start entirely discarded.
+  encoded_buffer->set_timestamp(kTimestamp + kDuration);

[acolwell GONE FROM CHROMIUM, 2014/07/24 19:22:14]

Shouldn't you be using  + 2 * kDuration here so it doesn't overlap the buffer
added above?

[DaleCurtis, 2014/07/29 01:35:09]

Done.

+  encoded_buffer->set_discard_padding(
+      std::make_pair(base::TimeDelta(), kDuration / 2));
+  decoded_buffer = CreateDecodedBuffer(kTestFrames);
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  EXPECT_EQ(kTimestamp + kDuration / 2, decoded_buffer->timestamp());
+  EXPECT_EQ(3 * kDuration / 4, decoded_buffer->duration());
+  EXPECT_EQ(3 * kTestFrames / 4, decoded_buffer->frame_count());
+
+  // Verify it was actually the second quarter of the buffer that was removed.
+  const int kDiscardFrames = kTestFrames / 4;
+  ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
+  ASSERT_FLOAT_EQ(
+      kDiscardFrames * 2 * kDataStep,
+      ExtractDecodedData(decoded_buffer, kDecoderDelay - kDiscardFrames));
+
+  // One last test to ensure carryover discard from the start works.
+  encoded_buffer->set_timestamp(kTimestamp + kDuration * 2);

[acolwell GONE FROM CHROMIUM, 2014/07/24 19:22:14]

Shouldn't this be *3?

[DaleCurtis, 2014/07/29 01:35:09]

Done.

+  encoded_buffer->set_discard_padding(DecoderBuffer::DiscardPadding());
+  decoded_buffer = CreateDecodedBuffer(kTestFrames);
+  ASSERT_FLOAT_EQ(0.0f, ExtractDecodedData(decoded_buffer, 0));
+  ASSERT_TRUE(discard_helper.ProcessBuffers(encoded_buffer, decoded_buffer));
+  EXPECT_EQ(kTimestamp + kDuration / 2 + 3 * kDuration / 4,
+            decoded_buffer->timestamp());
+  EXPECT_EQ(kDuration / 2, decoded_buffer->duration());
+  EXPECT_EQ(kTestFrames / 2, decoded_buffer->frame_count());
+  ASSERT_FLOAT_EQ(kTestFrames / 2 * kDataStep,
+                  ExtractDecodedData(decoded_buffer, 0));
 }
 
 TEST(AudioDiscardHelperTest, DelayedDiscardInitialDiscardAndDiscardPadding) {