Implemented parsing for H.264/AVC codec ids

media/base/video_codecs.cc

Index: media/base/video_codecs.cc
diff --git a/media/base/video_codecs.cc b/media/base/video_codecs.cc
index 7b3f77f04ecc451e2b831f010c47ea7a6ab26030..9e60cb66e900f4bfe92b4bc82c51b479f70962a8 100644
--- a/media/base/video_codecs.cc
+++ b/media/base/video_codecs.cc
@@ -5,6 +5,8 @@
 #include "media/base/video_codecs.h"
 
 #include "base/logging.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
 
 namespace media {
 
@@ -69,4 +71,96 @@ std::string GetProfileName(VideoCodecProfile profile) {
   return "";
 }
 
+bool ParseAVCCodecId(const std::string& codec_id,
+                     VideoCodecProfile* profile,
+                     uint8_t* level_idc) {
+  // Make sure we have avc1.xxxxxx or avc3.xxxxxx , where xxxxxx are hex digits
+  if (!base::StartsWith(codec_id, "avc1.", base::CompareCase::SENSITIVE) &&
+      !base::StartsWith(codec_id, "avc3.", base::CompareCase::SENSITIVE)) {
+    return false;
+  }
+  uint32_t elem = 0;
+  if (codec_id.size() != 11 ||
+      !base::HexStringToUInt(base::StringPiece(codec_id).substr(5), &elem)) {
+    DVLOG(4) << __FUNCTION__ << ": invalid avc codec id (" << codec_id << ")";
+    return false;
+  }
+
+  uint8_t level_byte = elem & 0xFF;
+  uint8_t constraints_byte = (elem >> 8) & 0xFF;
+  uint8_t profile_idc = (elem >> 16) & 0xFF;
+
+  // Check that the lower two bits of |constraints_byte| are zero (those are
+  // reserved and must be zero according to ISO IEC 14496-10).
+  if (constraints_byte & 3) {
+    DVLOG(4) << __FUNCTION__ << ": non-zero reserved bits in codec id "
+             << codec_id;
+    return false;
+  }
+
+  VideoCodecProfile out_profile = VIDEO_CODEC_PROFILE_UNKNOWN;
+  // profile_idc values for each profile are taken from ISO IEC 14496-10 and
+  // https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Profiles
+  switch (profile_idc) {
+    case 66:
+      out_profile = H264PROFILE_BASELINE;
+      break;
+    case 77:
+      out_profile = H264PROFILE_MAIN;
+      break;
+    case 83:
+      out_profile = H264PROFILE_SCALABLEBASELINE;
+      break;
+    case 86:
+      out_profile = H264PROFILE_SCALABLEHIGH;
+      break;
+    case 88:
+      out_profile = H264PROFILE_EXTENDED;
+      break;
+    case 100:
+      out_profile = H264PROFILE_HIGH;
+      break;
+    case 110:
+      out_profile = H264PROFILE_HIGH10PROFILE;
+      break;
+    case 118:
+      out_profile = H264PROFILE_MULTIVIEWHIGH;
+      break;
+    case 122:
+      out_profile = H264PROFILE_HIGH422PROFILE;
+      break;
+    case 128:
+      out_profile = H264PROFILE_STEREOHIGH;
+      break;
+    case 244:
+      out_profile = H264PROFILE_HIGH444PREDICTIVEPROFILE;
+      break;
+    default:
+      DVLOG(1) << "Warning: unrecognized AVC/H.264 profile " << profile_idc;
+      return false;
+  }
+
+  // TODO(servolk): Take into account also constraint set flags 3 through 5.
+  uint8_t constraint_set0_flag = (constraints_byte >> 7) & 1;
+  uint8_t constraint_set1_flag = (constraints_byte >> 6) & 1;
+  uint8_t constraint_set2_flag = (constraints_byte >> 5) & 1;
+  if (constraint_set2_flag && out_profile > H264PROFILE_EXTENDED) {
+    out_profile = H264PROFILE_EXTENDED;
+  }
+  if (constraint_set1_flag && out_profile > H264PROFILE_MAIN) {
+    out_profile = H264PROFILE_MAIN;
+  }
+  if (constraint_set0_flag && out_profile > H264PROFILE_BASELINE) {
+    out_profile = H264PROFILE_BASELINE;
+  }
+
+  if (level_idc)
+    *level_idc = level_byte;
+
+  if (profile)
+    *profile = out_profile;
+
+  return true;
+}
+
 }  // namespace media