diff --git a/trunk/src/protocol/srs_raw_avc.cpp b/trunk/src/protocol/srs_raw_avc.cpp
index a7c0155967..da98c6c67c 100644
--- a/trunk/src/protocol/srs_raw_avc.cpp
+++ b/trunk/src/protocol/srs_raw_avc.cpp
@@ -454,9 +454,23 @@ srs_error_t SrsRawAacStream::mux_sequence_header(SrsRawAacStreamCodec* codec, st
     // For example, AAC sampling_frequency_index is 3(48000HZ) or 4(44100HZ),
     // the sound_rate is always 3(44100HZ), if we covert sound_rate to
     // sampling_frequency_index, we may make mistake.
-    char samplingFrequencyIndex = codec->sampling_frequency_index;
-    if (samplingFrequencyIndex >= SrsAAcSampleRateNumbers) {
-        samplingFrequencyIndex = 4; // Default to 44100
+    uint8_t samplingFrequencyIndex = (uint8_t)codec->sampling_frequency_index;
+    if (samplingFrequencyIndex >= SrsAacSampleRateUnset) {
+        switch (codec->sound_rate) {
+            case SrsAudioSampleRate5512:
+                samplingFrequencyIndex = 0x0c; break;
+            case SrsAudioSampleRate11025:
+                samplingFrequencyIndex = 0x0a; break;
+            case SrsAudioSampleRate22050:
+                samplingFrequencyIndex = 0x07; break;
+            case SrsAudioSampleRate44100:
+                samplingFrequencyIndex = 0x04; break;
+            default:
+                break;
+        }
+    }
+    if (samplingFrequencyIndex >= SrsAacSampleRateUnset) {
+        return srs_error_new(ERROR_AAC_DATA_INVALID, "invalid sample index %d", samplingFrequencyIndex);
     }
 
     char chs[2];
@@ -470,9 +484,6 @@ srs_error_t SrsRawAacStream::mux_sequence_header(SrsRawAacStreamCodec* codec, st
     // samplingFrequencyIndex; 4 bslbf
     chs[0] |= (samplingFrequencyIndex >> 1) & 0x07;
     chs[1] = (samplingFrequencyIndex << 7) & 0x80;
-    if (samplingFrequencyIndex == 0x0f) {
-        return srs_error_new(ERROR_AAC_DATA_INVALID, "invalid sampling frequency index");
-    }
     // 7bits left.
     
     // channelConfiguration; 4 bslbf
diff --git a/trunk/src/utest/srs_utest_avc.cpp b/trunk/src/utest/srs_utest_avc.cpp
index 15b34f5902..9380632a99 100644
--- a/trunk/src/utest/srs_utest_avc.cpp
+++ b/trunk/src/utest/srs_utest_avc.cpp
@@ -405,6 +405,7 @@ VOID TEST(SrsAVCTest, AACMuxSequenceHeader)
         codec.aac_object = SrsAacObjectTypeAacMain;
         codec.channel_configuration = 1;
         codec.sound_rate = SrsAudioSampleRate22050;
+        codec.sampling_frequency_index = 7;
         HELPER_ASSERT_SUCCESS(h.mux_sequence_header(&codec, sh));
         EXPECT_EQ(2, sh.length());
         EXPECT_EQ(0x0b, (uint8_t)sh.at(0));
@@ -417,6 +418,7 @@ VOID TEST(SrsAVCTest, AACMuxSequenceHeader)
         codec.aac_object = SrsAacObjectTypeAacMain;
         codec.channel_configuration = 1;
         codec.sound_rate = SrsAudioSampleRate11025;
+        codec.sampling_frequency_index = 0xa;
         HELPER_ASSERT_SUCCESS(h.mux_sequence_header(&codec, sh));
         EXPECT_EQ(2, sh.length());
         EXPECT_EQ(0x0d, (uint8_t)sh.at(0));
@@ -426,7 +428,8 @@ VOID TEST(SrsAVCTest, AACMuxSequenceHeader)
     // Fail for invalid sampling rate.
     if (true) {
         SrsRawAacStream h; string sh; SrsRawAacStreamCodec codec;
-        codec.sampling_frequency_index = 0xf;
+        codec.aac_object = SrsAacObjectTypeAacMain;
+        codec.sampling_frequency_index = SrsAacSampleRateUnset;
         codec.sound_rate = SrsAudioSampleRateReserved;
         HELPER_EXPECT_FAILED(h.mux_sequence_header(&codec, sh));
     }
@@ -457,6 +460,33 @@ VOID TEST(SrsAVCTest, AACMuxSequenceHeader)
         codec.aac_object = SrsAacObjectTypeAacMain;
         codec.channel_configuration = 1;
         codec.sound_rate = SrsAudioSampleRate44100;
+        codec.sampling_frequency_index = 4;
+        HELPER_ASSERT_SUCCESS(h.mux_sequence_header(&codec, sh));
+        EXPECT_EQ(2, sh.length());
+        EXPECT_EQ(0x0a, (uint8_t)sh.at(0));
+        EXPECT_EQ(0x08, (uint8_t)sh.at(1));
+    }
+
+    // We ignored the sound_rate.
+    if (true) {
+        SrsRawAacStream h; string sh; SrsRawAacStreamCodec codec;
+        codec.aac_object = SrsAacObjectTypeAacMain;
+        codec.channel_configuration = 1;
+        codec.sound_rate = SrsAudioSampleRate22050;
+        codec.sampling_frequency_index = 4;
+        HELPER_ASSERT_SUCCESS(h.mux_sequence_header(&codec, sh));
+        EXPECT_EQ(2, sh.length());
+        EXPECT_EQ(0x0a, (uint8_t)sh.at(0));
+        EXPECT_EQ(0x08, (uint8_t)sh.at(1));
+    }
+
+    // Use sound_rate if sampling_frequency_index not set.
+    if (true) {
+        SrsRawAacStream h; string sh; SrsRawAacStreamCodec codec;
+        codec.aac_object = SrsAacObjectTypeAacMain;
+        codec.channel_configuration = 1;
+        codec.sound_rate = SrsAudioSampleRate44100;
+        codec.sampling_frequency_index = SrsAacSampleRateUnset;
         HELPER_ASSERT_SUCCESS(h.mux_sequence_header(&codec, sh));
         EXPECT_EQ(2, sh.length());
         EXPECT_EQ(0x0a, (uint8_t)sh.at(0));