Data corruption when writing very simple files with libebml 1.4.5 #312
Description
I wrote some code to try to write h.265 and AAC data to a file using libmatroska, and I kept running into a problem where the tracks were getting corrupted on output. Basically, the video track's info was getting jammed into the node for the audio track, so it had multiple track numbers, followed by a bunch of garbage.
And right now, I'm not even writing any frames, so that garbage output is all from the corrupted track data.
I spent basically an entire day trying to figure out what was wrong with my code, and finally in desperation, I built libmatroska and libebml from top-of-tree on GitHub and the bug went away. The only changes I made were adjusting all the last parameters in Render and a couple of other methods from true to EbmlElement::WriteSkipDefault, plus renaming timecode -> timestamp in various places, so this bug likely isn't being caused by my code, but rather by a bug in libebml 1.4.5.
I realize 1.4.5 was over a year ago, so I'm not sure if 1.4.5 is still supported in any way, but the code basically came straight out of libmatroska/tree/master/test/mdx/test6.cpp with only minor changes:
- Deleted the encryption and compression bits
- Added KaxVideoFlagInterlaced
- Added KaxVideoFieldOrder
- Used real codec IDs for H.265 and AAC
The track data from a working libebml looks like this
Tracks: (master) [90 bytes]
- TrackEntry: (master) [40 bytes]
-
- TrackNumber: 1
-
- TrackUID: 4
-
- TrackType: 2
-
- CodecID: 'A_AAC/MPEG4/MAIN'
-
- Audio: (master) [10 bytes]
-
-
- SamplingFrequency: 44100.000000
-
-
-
- BitDepth: 32
-
- TrackEntry: (master) [46 bytes]
-
- TrackNumber: 2
-
- TrackUID: 42
-
- TrackType: 1
-
- FlagLacing: 0
-
- CodecID: 'V_MPEG4/ISO/AVC'
-
- Video: (master) [14 bytes]
-
-
- FlagInterlaced: 2
-
-
-
- FieldOrder: 0
-
-
-
- PixelWidth: 3840
-
-
-
- PixelHeight: 2160
-
The bad data looks like this:
Tracks: (master) [216 bytes]
- TrackEntry: (master) [94 bytes]
-
- TrackNumber: 1
-
- TrackUID: 4
-
- TrackType: 2
-
- FlagEnabled: 1
-
- FlagDefault: 1
-
- FlagForced: 0
-
- FlagLacing: 1
-
- MinCache: 0
-
- TrackTimestampScale: 32779727273984.000000
-
- Language: 'eng'
-
- CodecID: 'A_AAC/MPEG4/MAIN'
-
- CodecDecodeAll: 86
-
- CodecDecodeAll: 0
-
- SeekPreRoll: 0
-
- Audio: (master) [17 bytes]
-
-
- SamplingFrequency: 44100.000000
-
-
-
- Channels: 1
-
-
-
- DummyElement: [52F1] [1 bytes]
-
-
-
- BitDepth: 32
-
-
- TrackNumber: 2
- DummyElement: [73C5] [1 bytes]
- DummyElement: [83] [1 bytes]
- DummyElement: [B9] [1 bytes]
- DummyElement: [88] [1 bytes]
- DummyElement: [55AA] [1 bytes]
- DummyElement: [9C] [1 bytes]
- DummyElement: [6DE7] [1 bytes]
- DummyElement: [23314F] [4 bytes]
- DummyElement: [22B59C] [3 bytes]
- DummyElement: [86] [15 bytes]
- DummyElement: [AA] [1 bytes]
- DummyElement: [AA] [1 bytes]
- DummyElement: [56BB] [1 bytes]
- DummyElement: [E0] [42 bytes]
I have no idea what's going on, but given that it doesn't happen in current sources, I'm assuming this is a bug. If libebml 1.x is still in any way supported, is there any chance that the bug fix that fixes this could be backported? I'm assuming there are reasons that 2.x isn't part of Homebrew yet, so...
Thanks.