media: Update VideoDmpReader handling of IAMF

This change modifies VideoDmpReader to parse the configuration of IAMF
dmp files, allowing it to craft an accurate MIME type string.

Bug: 485254424

Author: osagie98

starboard/shared/starboard/player/video_dmp_reader.cc

@@ -16,13 +16,16 @@
 
 #include <algorithm>
 #include <functional>
+#include <iomanip>
 
 #include "starboard/common/check_op.h"
 
 namespace starboard {
 
 namespace {
 
+constexpr uint8_t kIamfSequenceHeaderObu = 31;
+
 template <typename AccessUnit>
 int64_t CalculateAverageBitrate(const std::vector<AccessUnit>& access_units) {
   if (access_units.empty()) {
@@ -71,6 +74,29 @@ SbPlayerSampleInfo ConvertToPlayerSampleInfo(
   return sample_info;
 }
 
+// Helper function to read a LEB128 value.
+bool ReadLeb128(const uint8_t** data, const uint8_t* end, uint32_t* value) {
+  SB_DCHECK(data && *data);
+  SB_DCHECK(end);
+  SB_DCHECK(value);
+  *value = 0;
+  for (size_t i = 0; i < 5; ++i) {
+    if (*data >= end) {
+      return false;
+    }
+    uint8_t byte = *(*data)++;
+    if (i == 4 && (byte & 0x7f) > 0x0f) {
+      // A 32-bit value can't use more than 4 bits from the 5th LEB128 byte.
+      return false;
+    }
+    *value |= (uint32_t)(byte & 0x7f) << (i * 7);
+    if (!(byte & 0x80)) {
+      return true;
+    }
+  }
+  return false;
+}
+
 }  // namespace
 
 using std::placeholders::_1;
@@ -157,7 +183,16 @@ std::string VideoDmpReader::audio_mime_type() const {
       ss << "audio/wav; codecs=\"1\";";
       break;
     case kSbMediaAudioCodecIamf:
-      ss << "audio/mp4; codecs=\"iamf\";";
+      if (!dmp_info_.iamf_primary_profile.has_value()) {
+        return "";
+      }
+      // Only Opus IAMF substreams are currently supported.
+      ss << "audio/mp4; codecs=\"iamf.";
+      ss << std::setw(3) << std::setfill('0') << std::hex
+         << static_cast<int>(*dmp_info_.iamf_primary_profile) << "."
+         << std::setw(3) << std::setfill('0') << std::hex
+         << static_cast<int>(dmp_info_.iamf_additional_profile.value_or(0))
+         << ".Opus\";";
       break;
     default:
       SB_NOTREACHED() << "Unsupported audio codec: " << dmp_info_.audio_codec;
@@ -230,6 +265,52 @@ const AudioSampleInfo& VideoDmpReader::GetAudioSampleInfo(size_t index) {
   return au.audio_sample_info();
 }
 
+// Parse IAMF Config OBUs for the primary and additional profiles,
+// based on IAMF specification v1.0.0-errata.
+// https://aomediacodec.github.io/iamf/v1.1.0.html#codecsparameter.
+void VideoDmpReader::ParseIamfConfigOBU() {
+  if (dmp_info_.audio_codec != kSbMediaAudioCodecIamf) {
+    return;
+  }
+
+  if (audio_access_units_.empty()) {
+    SB_LOG(WARNING) << "IAMF stream has no access units.";
+    return;
+  }
+
+  const auto& data = audio_access_units_[0].data();
+  const uint8_t* ptr = data.data();
+  const uint8_t* end = ptr + data.size();
+
+  uint8_t header_byte = *ptr++;
+  uint8_t obu_type = (header_byte >> 3) & 0x1f;
+
+  uint32_t obu_size;
+  if (!ReadLeb128(&ptr, end, &obu_size)) {
+    SB_LOG(ERROR) << "Failed to parse OBU size.";
+    return;
+  }
+
+  if (static_cast<size_t>(end - ptr) < obu_size) {
+    SB_LOG(ERROR) << "OBU size exceeds access unit size.";
+    return;
+  }
+  const uint8_t* obu_end = ptr + obu_size;
+
+  if (obu_type == kIamfSequenceHeaderObu) {
+    if (ptr + sizeof(uint32_t) + 2 > obu_end) {
+      return;
+    }
+    // Skip ia_code (4 bytes).
+    ptr += sizeof(uint32_t);
+
+    dmp_info_.iamf_primary_profile = *ptr++;
+    dmp_info_.iamf_additional_profile = *ptr;
+  }
+  // The Sequence Header must be the first OBU. If it isn't found, leave the
+  // profile values unset.
+}
+
 void VideoDmpReader::ParseHeader(uint32_t* dmp_writer_version) {
   SB_DCHECK(dmp_writer_version);
   SB_DCHECK(!reverse_byte_order_.has_value());
@@ -305,6 +386,11 @@ void VideoDmpReader::Parse() {
   while (ParseOneRecord()) {
   }
 
+  if (dmp_info_.audio_codec == kSbMediaAudioCodecIamf &&
+      !dmp_info_.iamf_primary_profile.has_value()) {
+    ParseIamfConfigOBU();
+  }
+
   dmp_info_.audio_access_units_size = audio_access_units_.size();
   dmp_info_.audio_bitrate = CalculateAverageBitrate(audio_access_units_);
   dmp_info_.video_access_units_size = video_access_units_.size();

starboard/shared/starboard/player/video_dmp_reader.h

@@ -138,6 +138,8 @@ class VideoDmpReader {
     size_t audio_access_units_size = 0;
     int64_t audio_bitrate = 0;
     int audio_duration = 0;
+    std::optional<uint8_t> iamf_primary_profile;
+    std::optional<uint8_t> iamf_additional_profile;
 
     SbMediaVideoCodec video_codec = kSbMediaVideoCodecNone;
     size_t video_access_units_size = 0;
@@ -159,6 +161,7 @@ class VideoDmpReader {
   VideoDmpReader(const VideoDmpReader&) = delete;
   VideoDmpReader& operator=(const VideoDmpReader&) = delete;
 
+  void ParseIamfConfigOBU();
   void ParseHeader(uint32_t* dmp_writer_version);
   bool ParseOneRecord();
   void Parse();