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Handle variable size header for the MDAT atom [#261]
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@Zeugma440
Zeugma440 committed Apr 17, 2024
1 parent 5111dfc commit fdbb779
Showing 1 changed file with 40 additions and 17 deletions.
57 changes: 40 additions & 17 deletions ATL/AudioData/IO/MP4.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -373,7 +373,7 @@ private bool readMP4(BinaryReader source, ReadTagParams readTagParams)
}

// === Physical data header
if (0 == navigateToAtom(source, "mvhd"))
if (0 == navigateToAtom(source.BaseStream, "mvhd"))
{
LogDelegator.GetLogDelegate()(Log.LV_ERROR, "mvhd atom could not be found; aborting read");
return false;
Expand Down Expand Up @@ -442,14 +442,16 @@ private bool readMP4(BinaryReader source, ReadTagParams readTagParams)
// == Audio binary data, chapter or subtitle data
// Per convention, audio binary data always seems to be in the 1st mdat atom of the file
source.BaseStream.Seek(sizeInfo.ID3v2Size, SeekOrigin.Begin);
uint mdatSize = navigateToAtom(source, "mdat");
var mdatAtomData = navigateToAtomSize(source.BaseStream, "mdat");
uint mdatSize = mdatAtomData.Item1;
int mdatHeaderSize = mdatAtomData.Item2;
if (0 == mdatSize)
{
LogDelegator.GetLogDelegate()(Log.LV_ERROR, "mdat atom could not be found; aborting read");
return false;
}
long mdatOffset = source.BaseStream.Position;
AudioDataOffset = mdatOffset - 8;
AudioDataOffset = mdatOffset - mdatHeaderSize;
AudioDataSize = mdatSize;
bitrate = (int)Math.Round(mdatSize * 8 / calculatedDurationMs * 1000.0, 0);

Expand Down Expand Up @@ -534,23 +536,25 @@ private bool readMP4(BinaryReader source, ReadTagParams readTagParams)
// On some files, there's a single MDAT atom that contains both chapter references and audio data
// => limit zone size to the actual size of the chapters
// TODO handle non-contiguous chapters (e.g. chapter data interleaved with audio data)
if (minChapterOffset >= source.BaseStream.Position && minChapterOffset < source.BaseStream.Position - 8 + mdatSize)
if (minChapterOffset >= source.BaseStream.Position && minChapterOffset < source.BaseStream.Position - mdatHeaderSize + mdatSize)
{
chapMdatOffset = source.BaseStream.Position - 8;
chapMdatOffset = source.BaseStream.Position - mdatHeaderSize;
// Zone size = size of chapter data (text and pictures)
chapMdatDataSize = chapterTextSize + chapterPictureSize;
chapMdatChapSize = mdatSize;
}

source.BaseStream.Seek(mdatSize - 8, SeekOrigin.Current);
mdatSize = navigateToAtom(source, "mdat");
source.BaseStream.Seek(mdatSize - mdatHeaderSize, SeekOrigin.Current);
mdatAtomData = navigateToAtomSize(source.BaseStream, "mdat");
mdatSize = mdatAtomData.Item1;
mdatHeaderSize = mdatAtomData.Item2;
} while (mdatSize > 0);
} // QT chapters are present

// Memorize the definitive chapter data location as a zone
if (chapMdatDataSize > -1)
{
structureHelper.AddZone(chapMdatOffset + 8, chapMdatDataSize, ZONE_MP4_QT_CHAP_MDAT);
structureHelper.AddZone(chapMdatOffset + mdatHeaderSize, chapMdatDataSize, ZONE_MP4_QT_CHAP_MDAT);
structureHelper.AddSize(chapMdatOffset, chapMdatChapSize, ZONE_MP4_QT_CHAP_MDAT);
}
} // Write mode
Expand All @@ -562,7 +566,7 @@ private bool readMP4(BinaryReader source, ReadTagParams readTagParams)
// == Padding management
// Seek the generic padding atom
source.BaseStream.Seek(sizeInfo.ID3v2Size, SeekOrigin.Begin);
initialPaddingSize = navigateToAtom(source, "free");
initialPaddingSize = navigateToAtom(source.BaseStream, "free");
if (initialPaddingSize > 0) tagData.PaddingSize = initialPaddingSize;

if (readTagParams.PrepareForWriting)
Expand Down Expand Up @@ -613,7 +617,7 @@ long moovSize

string trackZoneName = "";

uint trakSize = navigateToAtom(source, "trak");
uint trakSize = navigateToAtom(source.BaseStream, "trak");
if (0 == trakSize)
{
LogDelegator.GetLogDelegate()(Log.LV_DEBUG, "total tracks found : " + (currentTrakIndex - 1));
Expand All @@ -622,7 +626,7 @@ long moovSize
var trakPosition = source.BaseStream.Position - 8;

// Read track ID
if (0 == navigateToAtom(source, "tkhd"))
if (0 == navigateToAtom(source.BaseStream, "tkhd"))
{
LogDelegator.GetLogDelegate()(Log.LV_DEBUG, "trak.tkhd atom could not be found; aborting read on track " + currentTrakIndex);
source.BaseStream.Seek(trakPosition + trakSize, SeekOrigin.Begin);
Expand Down Expand Up @@ -861,7 +865,7 @@ long moovSize
{
uint nbSizes = StreamUtils.DecodeBEUInt32(source.ReadBytes(4));
uint max = 0;
uint min = UInt32.MaxValue;
uint min = uint.MaxValue;

for (int i = 0; i < nbSizes; i++)
{
Expand Down Expand Up @@ -1557,6 +1561,24 @@ private static uint navigateToAtom(BinaryReader source, string atomKey)
}

private static uint navigateToAtom(Stream source, string atomKey)
{
return navigateToAtomSize(source, atomKey).Item1;
}

/// <summary>
/// Look for the atom segment starting with the given key, at the current atom level
/// Returns with Source positioned right after the atom header, on the 1st byte of data
///
/// Warning : stream must be positioned at the end of a previous atom before being called
/// </summary>
/// <param name="source">Source to read from</param>
/// <param name="atomKey">Atom key to look for (e.g. "udta")</param>
/// <returns>
/// - Item1 : If atom found : raw size of the atom (including the already-read 8-byte header);
/// If atom not found : 0
/// - Item2 : Size of the atom header (may vary if using the 64-bit variant)
/// </returns>
private static Tuple<uint, int> navigateToAtomSize(Stream source, string atomKey)
{
long atomSize = 0;
string atomHeader;
Expand All @@ -1567,7 +1589,7 @@ private static uint navigateToAtom(Stream source, string atomKey)

do
{
atomHeaderSize = 16;
atomHeaderSize = 8;
if (!first) source.Seek(atomSize - 8, SeekOrigin.Current);
source.Read(data, 0, 4);
atomSize = StreamUtils.DecodeBEUInt32(data);
Expand All @@ -1581,7 +1603,7 @@ private static uint navigateToAtom(Stream source, string atomKey)
}

if (first) first = false;
if (++iterations > 100) return 0;
if (++iterations > 100) return new Tuple<uint, int>(0, atomHeaderSize);
} while (!atomKey.Equals(atomHeader) && source.Position + atomSize - atomHeaderSize < source.Length);

if (source.Position + atomSize - atomHeaderSize > source.Length)
Expand All @@ -1591,13 +1613,14 @@ private static uint navigateToAtom(Stream source, string atomKey)
{
uint actualSize = (uint)(source.Length - source.Position + atomHeaderSize);
LogDelegator.GetLogDelegate()(Log.LV_WARNING, "atom " + atomKey + " has been declared with an incorrect size; using its actual size (" + actualSize + " bytes)");
return actualSize;
return new Tuple<uint, int>(actualSize, atomHeaderSize);
}
// atom not found
return 0;
return new Tuple<uint, int>(0, atomHeaderSize);
}

return atomKey.Equals(atomHeader) ? (uint)atomSize : 0;
var result = atomKey.Equals(atomHeader) ? (uint)atomSize : 0;
return new Tuple<uint, int>(result, atomHeaderSize);
}


Expand Down

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