Feature/12bit pixel format support

[roshan-ku]

Description

Adds support for 12-bit pixel formats in the dvledtx transmitter, enabling higher bit-depth video transmission over ST 2110-20 via MTL.
Supported 12-bit Formats:

Format	Chroma	Color Space
yuv422p12le	4:2:2	YUV
yuv444p12le	4:4:4	YUV
gbrp12le	4:4:4	RGB

Checklist

Code Quality

• Code follows project style guidelines
• No unnecessary debug logs or commented-out code
• No hardcoded values / secrets

Testing

• Unit test added/modified accordingly
• Perform manual basic sanity testing at system level

Review Readiness

• PR title and description are clear and meaningful
• Story/Task IDs are linked

Documentation

• README or relevant docs updated (if applicable)

Security

• No sensitive data exposed (keys, passwords, tokens)
• Input validation added where needed

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Documentation content changes
• Testing
• Other... Please describe:

[Copilot]

Pull request overview

Adds 12-bit pixel format support end-to-end (config validation/parsing, MTL mapping, docs, and unit tests) so dvledtx can transmit higher bit-depth video over ST 2110-20 via MTL.

Changes:

• Extend config reader validation and string→AVPixelFormat mapping to accept yuv422p12le, yuv444p12le, and gbrp12le.
• Extend MTL TX format mapping (AVPixelFormat → st_frame_fmt / st20_fmt) for 12-bit planar formats.
• Update unit tests and README supported-format documentation accordingly.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test_mtl_tx.c	Adds unit tests for new 12-bit transport-format mappings (and should also cover input-format mappings).
tests/test_config_reader.c	Extends supported-format validation test coverage to include the new 12-bit format strings.
src/util/config_reader.c	Adds new 12-bit formats to validation and applies them into app->fmt during config load.
src/mtl/mtl_tx.c	Adds 12-bit mappings for MTL input/transport formats.
README.md	Reworks supported formats into a table and adds 12-bit format entries.

Comments suppressed due to low confidence (2)

src/util/config_reader.c:604

• validate_tx_config() allows video.fmt to be omitted (empty string), but load_and_apply_config() unconditionally strcmp()s config.fmt and errors out when it’s empty. This makes a config that omits fmt pass validation but fail to load. Consider treating empty fmt as the documented default (yuv422p10le) when applying the config (or make fmt required in validation).

    if (strcmp(config.fmt, "yuv422p10le") == 0)       app->fmt = AV_PIX_FMT_YUV422P10LE;
    else if (strcmp(config.fmt, "yuv420") == 0)        app->fmt = AV_PIX_FMT_YUV420P;
    else if (strcmp(config.fmt, "yuv444p10le") == 0)  app->fmt = AV_PIX_FMT_YUV444P10LE;
    else if (strcmp(config.fmt, "gbrp10le") == 0)     app->fmt = AV_PIX_FMT_GBRP10LE;
    else if (strcmp(config.fmt, "yuv422p12le") == 0)  app->fmt = AV_PIX_FMT_YUV422P12LE;
    else if (strcmp(config.fmt, "yuv444p12le") == 0)  app->fmt = AV_PIX_FMT_YUV444P12LE;
    else if (strcmp(config.fmt, "gbrp12le") == 0)     app->fmt = AV_PIX_FMT_GBRP12LE;
    else {
        LOG_ERROR("Unsupported pixel format '%s'", config.fmt);
        return -1;
    }

tests/test_mtl_tx.c:100

• New 12-bit support updates get_input_format() as well, but the unit tests added here only cover get_transport_format(). Adding a simple test for the new get_input_format() mappings would prevent regressions (and makes test header comments about covered formats accurate).

static void test_get_transport_format_gbrp12le(void **state)
{
    (void)state;
    assert_int_equal(get_transport_format(AV_PIX_FMT_GBRP12LE),
                     ST20_FMT_RGB_12BIT);
}

static void test_get_transport_format_unknown_returns_error(void **state)
{
    (void)state;
    /* AV_PIX_FMT_NONE hits the default branch → error (-1) */
    assert_int_equal((int)get_transport_format(AV_PIX_FMT_NONE), -1);
}

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