Add Common Encryption support to BMFF, including subsample decryption.

media/mp4/box_definitions.cc

Index: media/mp4/box_definitions.cc
diff --git a/media/mp4/box_definitions.cc b/media/mp4/box_definitions.cc
index 5d18c32182f0db20f236ed283af903a75fa213d5..fb9723006fb8aa7528092ddb9113d5bedc5a329d 100644
--- a/media/mp4/box_definitions.cc
+++ b/media/mp4/box_definitions.cc
@@ -85,7 +85,7 @@ SchemeType::~SchemeType() {}
 FourCC SchemeType::BoxType() const { return FOURCC_SCHM; }
 
 bool SchemeType::Parse(BoxReader* reader) {
-  RCHECK(reader->SkipBytes(4) &&
+  RCHECK(reader->ReadFullBoxHeader() &&

[ddorwin, 2012/06/26 06:09:19]

Why all the RCHECKs? Macros are discouraged, and this one actually has a return
in it, which is really unexpected.
I assume there was a specific reason it was allowed in the previous CL?

[strobe_, 2012/06/27 02:01:21]

The alternatives were worse. ;)

There are some tricky cases during parsing where we might be exposed to memory
corruption or otherwise produce invalid data. We catch those by using
WARN_UNUSED_RESULT on common functions that might return an error indicating
that parsing should immediately halt with an error state. The hierarchical
nature of BMFF means that even in this very simple parser, RCHECK gets used
quite a bit. Replacing each of those instances with the corresponding four-line
definition turned out to be really messy, and we also had a couple places where
the messiness of the code hid logic bugs in the original effort.

          reader->ReadFourCC(&type) &&
          reader->Read4(&version));
   RCHECK(type == FOURCC_CENC);
@@ -100,7 +100,8 @@ FourCC TrackEncryption::BoxType() const { return FOURCC_TENC; }
 
 bool TrackEncryption::Parse(BoxReader* reader) {
   uint8 flag;
-  RCHECK(reader->SkipBytes(2) &&
+  RCHECK(reader->ReadFullBoxHeader() &&
+         reader->SkipBytes(2) &&
          reader->Read1(&flag) &&
          reader->Read1(&default_iv_size) &&
          reader->ReadVec(&default_kid, 16));
@@ -126,9 +127,10 @@ ProtectionSchemeInfo::~ProtectionSchemeInfo() {}
 FourCC ProtectionSchemeInfo::BoxType() const { return FOURCC_SINF; }
 
 bool ProtectionSchemeInfo::Parse(BoxReader* reader) {
-  return reader->ScanChildren() &&
+  RCHECK(reader->ScanChildren() &&
          reader->ReadChild(&type) &&
-         reader->ReadChild(&info);
+         reader->ReadChild(&info));
+  return true;
 }
 
 MovieHeader::MovieHeader()
@@ -362,19 +364,12 @@ bool VideoSampleEntry::Parse(BoxReader* reader) {
          reader->Read2(&height) &&
          reader->SkipBytes(50));
 
+  // TODO(strobe): Finalize format signaling for encrypted media
+  // (http://crbug.com/132351). For now, we assume that every video track is
+  // AVC, and that any track may have a Common Encryption header regardless of
+  // format.
   RCHECK(reader->ScanChildren());
-  if (format == FOURCC_ENCV) {
-    RCHECK(reader->ReadChild(&sinf));
-  }
-
-  // TODO(strobe): finalize format signaling for encrypted media
-  // (http://crbug.com/132351)
-  //
-  //  if (format == FOURCC_AVC1 ||
-  //      (format == FOURCC_ENCV &&
-  //       sinf.format.format == FOURCC_AVC1)) {
-    RCHECK(reader->ReadChild(&avcc));
-  //  }
+  RCHECK(reader->ReadChild(&avcc) && reader->MaybeReadChild(&sinf));
   return true;
 }
 
@@ -404,10 +399,8 @@ bool AudioSampleEntry::Parse(BoxReader* reader) {
   // Convert from 16.16 fixed point to integer
   samplerate >>= 16;
 
-  RCHECK(reader->ScanChildren());
-  if (format == FOURCC_ENCA) {
-    RCHECK(reader->ReadChild(&sinf));
-  }
+  RCHECK(reader->ScanChildren() &&
+         reader->MaybeReadChild(&sinf));
   return true;
 }