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Fix issues in BitstreamConverter #23174

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Fix issues in BitstreamConverter #23174

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samnazarko
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Description

This fixes a pointer arithmetic issue and also parses mvcC atom for 3D playback.

Motivation and context

How has this been tested?

This has been tested on OSMC Vero 4K / 4K + devices since 2020.

What is the effect on users?

Screenshots (if appropriate):

Types of change

  • Bug fix (non-breaking change which fixes an issue)
  • Clean up (non-breaking change which removes non-working, unmaintained functionality)
  • Improvement (non-breaking change which improves existing functionality)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that will cause existing functionality to change)
  • Cosmetic change (non-breaking change that doesn't touch code)
  • None of the above (please explain below)

Checklist:

  • My code follows the Code Guidelines of this project
  • My change requires a change to the documentation, either Doxygen or wiki
  • I have updated the documentation accordingly
  • I have read the Contributing document
  • I have added tests to cover my change
  • All new and existing tests passed

lrusak
lrusak reviewed Apr 19, 2023
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I know there is a lot of legacy code going on here and a lot of C-isms but it would be great if you could update the PR to use current standards. I would also love it if we could improve the class as a whole by using human readable parsing, removing goto's and the lot.

xbmc/utils/BitstreamConverter.cpp
@@ -726,6 +727,18 @@ bool CBitstreamConverter::BitstreamConvertInitAVC(void *in_extradata, int in_ext
if (unit_nb)
pps_seen = 1;
}

if (!unit_nb && !mvc_done++)
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I know you were following the pattern but generally ints either need to be compared directly or casted to bool. I also recommend using a bool when wanting a boolean check.

Suggested change
if (!unit_nb && !mvc_done++)
if (unit_nb == 0 && !mvc_done)

xbmc/utils/BitstreamConverter.cpp
@@ -678,6 +678,7 @@ bool CBitstreamConverter::BitstreamConvertInitAVC(void *in_extradata, int in_ext
uint16_t unit_size;
uint32_t total_size = 0;
uint8_t *out = NULL, unit_nb, sps_done = 0, sps_seen = 0, pps_seen = 0;
uint8_t mvc_done = 0;
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Suggested change
uint8_t mvc_done = 0;
bool mvcDone{false};

xbmc/utils/BitstreamConverter.cpp
unit_nb = *extradata++ & 0x1f; // number of sps unit(s)
sps_done = 0;
pps_seen = 0;
}
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Suggested change
}
mvcDone = true;
}

xbmc/utils/BitstreamConverter.cpp

if (!unit_nb && !mvc_done++)
{
if (in_extrasize - total_size > 14 && memcmp(extradata + 8, "mvcC", 4) == 0)
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Generally magic numbers are frowned upon. Please use constexpr int's to help with human readable values. In reality it would just be nice if we could define a structure for the extradata so we don't need to do all this magic number jumping around but I'll leave that as a future wish.

Suggested change
if (in_extrasize - total_size > 14 && memcmp(extradata + 8, "mvcC", 4) == 0)
constexpr int MINIMUM_SIZE{14};
constexpr int HEADER_OFFSET{8};
if (in_extrasize - total_size > MINIMUM_SIZE && memcmp(extradata + HEADER_OFFSET, "mvcC", strlen("mvcC")) == 0)

xbmc/utils/BitstreamConverter.cpp
// start over; take SPS and PPS from the mvcC atom
extradata += 12 + 5; // skip over mvcC atom header
unit_nb = *extradata++ & 0x1f; // number of sps unit(s)
sps_done = 0;
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It would be a gold star if you could (possibly in a future PR) convert these to bool.

xbmc/utils/BitstreamConverter.cpp
{
// start over; take SPS and PPS from the mvcC atom
extradata += 12 + 5; // skip over mvcC atom header
unit_nb = *extradata++ & 0x1f; // number of sps unit(s)
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more magic?

xbmc/utils/BitstreamConverter.cpp
if (in_extrasize - total_size > 14 && memcmp(extradata + 8, "mvcC", 4) == 0)
{
// start over; take SPS and PPS from the mvcC atom
extradata += 12 + 5; // skip over mvcC atom header
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magic everywhere!

@lrusak lrusak added Type: Fix non-breaking change which fixes an issue Component: Video v21 Omega labels Apr 19, 2023
@lrusak lrusak added this to the Omega 21.0 Alpha 2 milestone Apr 19, 2023
@jenkins4kodi
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I've made some formatting changes to meet the current code style. The diffs are available in the following links:

For more information please see our current code style guidelines.

@fuzzard fuzzard added v22 "P" and removed v21 Omega labels Feb 26, 2024
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@samnazarko @jenkins4kodi @lrusak @fuzzard @tanio99