[audio][eac3] Support EAC3 with small frames
EAC3 can have 1,2,3 or 6 audio blocks per sync frame.
The old code only supported 6 audio blocks per sync frame.
So streams with fewer blocks were not aligned correctly
in the SPDIF data burst. See IEC61937-3 spec P5.3.3.
The code now tracks how many blocks have been accumulated
for each possible substream.
Bug: 18315783
Change-Id: I75dbedeb69a597a877b2b68c6be23c831ae119b6
Signed-off-by: Phil Burk <philburk@google.com>
diff --git a/audio_utils/spdif/FrameScanner.cpp b/audio_utils/spdif/FrameScanner.cpp
index f12e538..5a6e21f 100644
--- a/audio_utils/spdif/FrameScanner.cpp
+++ b/audio_utils/spdif/FrameScanner.cpp
@@ -15,7 +15,7 @@
** limitations under the License.
*/
-#define LOG_TAG "AudioHardwareTungsten"
+#define LOG_TAG "AudioSPDIF"
#include <utils/Log.h>
#include <audio_utils/spdif/FrameScanner.h>
@@ -104,13 +104,13 @@
: FrameScanner(SPDIF_DATA_TYPE_AC3)
, mState(STATE_EXPECTING_SYNC_1)
, mBytesSkipped(0)
- , mLengthCode(0)
, mAudioBlocksPerSyncFrame(6)
, mCursor(AC3_SYNCWORD_SIZE) // past sync word
, mStreamType(0)
, mSubstreamID(0)
, mFormatDumpCount(0)
{
+ memset(mSubstreamBlockCounts, 0, sizeof(mSubstreamBlockCounts));
// Define beginning of syncinfo for getSyncAddress()
mHeaderBuffer[0] = kAC3SyncByte1;
mHeaderBuffer[1] = kAC3SyncByte2;
@@ -125,14 +125,36 @@
return mRateMultiplier * AC3_MAX_BLOCKS_PER_SYNC_FRAME_BLOCK * AC3_PCM_FRAMES_PER_BLOCK;
}
+void AC3FrameScanner::resetBurst()
+{
+ for (int i = 0; i < EAC3_MAX_SUBSTREAMS; i++) {
+ if (mSubstreamBlockCounts[i] >= AC3_MAX_BLOCKS_PER_SYNC_FRAME_BLOCK) {
+ mSubstreamBlockCounts[i] -= AC3_MAX_BLOCKS_PER_SYNC_FRAME_BLOCK;
+ } else if (mSubstreamBlockCounts[i] > 0) {
+ ALOGW("EAC3 substream[%d] has only %d audio blocks!",
+ i, mSubstreamBlockCounts[i]);
+ mSubstreamBlockCounts[i] = 0;
+ }
+ }
+}
+
// per IEC 61973-3 Paragraph 5.3.3
+// We have to send 6 audio blocks on all active substreams.
+// Substream zero must be the first.
+// We don't know if we have all the blocks we need until we see
+// the 7th block of substream#0.
bool AC3FrameScanner::isFirstInBurst()
{
if (mDataType == SPDIF_DATA_TYPE_E_AC3) {
- return (((mStreamType == 0) || (mStreamType == 2)) && (mSubstreamID == 0));
- } else {
- return false; // For AC3 just flush at end.
+ if (((mStreamType == 0) || (mStreamType == 2))
+ && (mSubstreamID == 0)
+ // The ">" is intentional. We have to see the beginning of the block
+ // in the next burst before we can send the current burst.
+ && (mSubstreamBlockCounts[0] > AC3_MAX_BLOCKS_PER_SYNC_FRAME_BLOCK)) {
+ return true;
+ }
}
+ return false;
}
bool AC3FrameScanner::isLastInBurst()
@@ -165,14 +187,9 @@
// The names fscod, frmsiz are from the AC3 spec.
int fscod = mHeaderBuffer[4] >> 6;
if (mDataType == SPDIF_DATA_TYPE_E_AC3) {
- mStreamType = mHeaderBuffer[2] >> 6;
+ mStreamType = mHeaderBuffer[2] >> 6; // strmtyp in spec
mSubstreamID = (mHeaderBuffer[2] >> 3) & 0x07;
- // Print enough so we can see all the substreams.
- ALOGD_IF((mFormatDumpCount < 3*8 ),
- "EAC3 strmtyp = %d, substreamid = %d",
- mStreamType, mSubstreamID);
-
// Frame size is explicit in EAC3. Paragraph E2.3.1.3
int frmsiz = ((mHeaderBuffer[2] & 0x07) << 8) + mHeaderBuffer[3];
mFrameSizeBytes = (frmsiz + 1) * sizeof(int16_t);
@@ -191,8 +208,17 @@
numblkscod = (mHeaderBuffer[4] >> 4) & 0x03;
}
mRateMultiplier = EAC3_RATE_MULTIPLIER; // per IEC 61973-3 Paragraph 5.3.3
- // TODO Don't send data burst until we have 6 blocks per substream.
+ // Don't send data burst until we have 6 blocks per substream.
mAudioBlocksPerSyncFrame = kEAC3BlocksPerFrameTable[numblkscod];
+ // Keep track of how many audio blocks we have for each substream.
+ // This should be safe because mSubstreamID is ANDed with 0x07 above.
+ // And the array is allocated as [8].
+ mSubstreamBlockCounts[mSubstreamID] += mAudioBlocksPerSyncFrame;
+
+ // Print enough so we can see all the substreams.
+ ALOGD_IF((mFormatDumpCount < 3*8 ),
+ "EAC3 mStreamType = %d, mSubstreamID = %d",
+ mStreamType, mSubstreamID);
} else { // regular AC3
// Extract sample rate and frame size from codes.
unsigned int frmsizcod = mHeaderBuffer[4] & 0x3F; // frame size code
@@ -211,7 +237,6 @@
}
mAudioBlocksPerSyncFrame = 6;
}
- mLengthCode = 8 * mFrameSizeBytes; // size in bits
ALOGI_IF((mFormatDumpCount == 0),
"AC3 frame rate = %d * %d, size = %d, audioBlocksPerSyncFrame = %d\n",
mSampleRate, mRateMultiplier, mFrameSizeBytes, mAudioBlocksPerSyncFrame);