Return parsed sample frequency of ADTS header

media/formats/mpeg/adts_header_parser.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/formats/mpeg/adts_header_parser.h"
 
 #include <algorithm>
 #include <vector>
 #include "base/logging.h"
 #include "media/base/audio_codecs.h"
@@ skipping 11 matching lines @@
 }
 
 size_t ExtractAdtsChannelConfig(const uint8_t* adts_header) {
   return (((adts_header[3] >> 6) & 0x3) | ((adts_header[2] & 0x1) << 2));
 }
 
 }  // namespace (anonymous)
 
 bool ParseAdtsHeader(const uint8_t* adts_header,
                      bool is_sbr,
-                     AudioDecoderConfig* config) {
+                     AudioDecoderConfig* config,
+                     size_t* orig_sample_freq) {
   DCHECK(adts_header);
+  DCHECK(orig_sample_freq);
 
   size_t frequency_index = ExtractAdtsFrequencyIndex(adts_header);
   if (frequency_index >= kADTSFrequencyTableSize) {
     // Frequency index 13 & 14 are reserved
     // while 15 means that the frequency is explicitly written
     // (not supported).
     return false;
   }
 
   size_t channel_configuration = ExtractAdtsChannelConfig(adts_header);
   if (channel_configuration == 0 ||
       channel_configuration >= kADTSChannelLayoutTableSize) {
     // TODO(damienv): Add support for inband channel configuration.
     return false;
   }
 
   // TODO(damienv): support HE-AAC frequency doubling (SBR)
   // based on the incoming ADTS profile.
   int samples_per_second = kADTSFrequencyTable[frequency_index];
   int adts_profile = (adts_header[2] >> 6) & 0x3;
 
   // The following code is written according to ISO 14496 Part 3 Table 1.11 and
   // Table 1.22. (Table 1.11 refers to the capping to 48000, Table 1.22 refers
   // to SBR doubling the AAC sample rate.)
   // TODO(damienv) : Extend sample rate cap to 96kHz for Level 5 content.
   int extended_samples_per_second =
       is_sbr ? std::min(2 * samples_per_second, 48000) : samples_per_second;
+  *orig_sample_freq = samples_per_second;
 
   // The following code is written according to ISO 14496 Part 3 Table 1.13 -
   // Syntax of AudioSpecificConfig.
   uint16_t extra_data_int = static_cast<uint16_t>(
       // Note: adts_profile is in the range [0,3], since the ADTS header only
       // allows two bits for its value.
       ((adts_profile + 1) << 11) +
       // frequency_index is [0..13], per early out above.
       (frequency_index << 7) +
       // channel_configuration is [0..7], per early out above.
       (channel_configuration << 3));
   std::vector<uint8_t> extra_data;
   extra_data.push_back(static_cast<uint8_t>(extra_data_int >> 8));
   extra_data.push_back(static_cast<uint8_t>(extra_data_int & 0xff));
 
   DCHECK(config);
   *config = AudioDecoderConfig(kCodecAAC, kSampleFormatS16,
                                kADTSChannelLayoutTable[channel_configuration],
                                extended_samples_per_second, extra_data,
                                Unencrypted());
 
   return true;
 }
 
 }  // namespace media