[1.x] KaxBlock: rework EBML lacing sizes in SCOPE_PARTIAL_DATA mode#237
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robUx4 wants to merge 4 commits into
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[1.x] KaxBlock: rework EBML lacing sizes in SCOPE_PARTIAL_DATA mode#237robUx4 wants to merge 4 commits into
robUx4 wants to merge 4 commits into
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robUx4
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Apr 28, 2026
mbunkus
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Jul 5, 2026
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The changes are fine IMO & pass my test suite. I only have to small requests, posted at appropriate places.
| Result += input.read(cursor, FrameNum*4); | ||
| FrameSize = ReadCodedSizeValue(cursor, SizeRead, SizeUnknown); | ||
| { | ||
| auto EBMLCodecLength = [](binary buf) { |
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I'd prefer this to be a top-level function in an anonymous namespace. There's really no need to make it a lambda; it only makes the function longer & slightly harder to read. Thanks.
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I created a static function on top of the file. IMO that's something that should be provided by libebml. But I guess that should be for the v2.0.
| if (FrameNum == 0) | ||
| Index = 0; | ||
| else { | ||
| binary length_buf[8]; |
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Can you please fix the indentation of this whole block? Thanks.
We only read the bytes that correspond to frame sizes, rather than a guesstimate of how much data we are going to need. That's what the SCOPE_PARTIAL_DATA mode is about. This is already the case for LACING_XIPH. And we don't need a buffer allocation.
The spec [^1] is not clear whether when there is a single frame in the lace the size of the frame should be written. However it is forbidden to put a single frame in a lace [^2]. libmatroska doesn't support it. libavformat doesn't support lacing writing. However the last frame size is never written in any lace, so that's the first one when there's only one frame. [^1]: https://www.rfc-editor.org/rfc/rfc9559#section-10.3.3 [^2]: https://www.rfc-editor.org/rfc/rfc9559#section-10.3
No functional changes.
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We only read the bytes that correspond to frame sizes, rather
than a guesstimate of how much data we are going to need.
That's what the
SCOPE_PARTIAL_DATAmode is about. This is already the casefor
LACING_XIPH. And we don't need a buffer allocation.And throw when the EBML length difference gives a negative frame length.