[{"id":39763,"web_url":"https://patchwork.libcamera.org/comment/39763/","msgid":"","date":"2026-07-20T13:11:42","subject":"Re: [PATCH v2 1/1] gstreamer: Prefer non-raw (i.e. non-Bayer)\n\tformats in caps negotiation","submitter":{"id":216,"url":"https://patchwork.libcamera.org/api/people/216/","name":"Barnabás Pőcze","email":"barnabas.pocze@ideasonboard.com"},"content":"Hi\n\n2026. 07. 20. 13:10 keltezéssel, David Plowman írta:\n> Existing code was preferring fixed size outputs over ones with ranges,\n> resulting in raw output formats being preferred even when applications\n> (\"cheese\" is one such example) aren't expecting them and subsequently\n> fail.\n> \n> The revised version still prefers fixed size outputs over ones with\n> ranges, but will prefer non-raw (meaning non-Bayer) formats where\n> these are available. This still allows applications that explicitly\n> request raw formats to get them, but other applications will normally\n> get non-raw formats which they handle better.\n> \n> Fixes, for example, \"cheese\" on Raspberry Pi.\n> \n> Signed-off-by: David Plowman \n> ---\n> src/gstreamer/gstlibcamera-utils.cpp | 125 ++++++++++++++++++++-------\n> src/gstreamer/gstlibcamera-utils.h | 2 +-\n> src/gstreamer/gstlibcamerasrc.cpp | 3 +-\n> 3 files changed, 97 insertions(+), 33 deletions(-)\n> \n> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp\n> index 6541d478c..f0f128880 100644\n> --- a/src/gstreamer/gstlibcamera-utils.cpp\n> +++ b/src/gstreamer/gstlibcamera-utils.cpp\n> @@ -9,6 +9,7 @@\n> #include \"gstlibcamera-utils.h\"\n> \n> #include \n> +#include \n> \n> #include \n> #include \n> @@ -435,61 +436,121 @@ gst_libcamera_stream_configuration_to_caps(const StreamConfiguration &stream_cfg\n> \treturn caps;\n> }\n> \n> -void gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> +/*\n> + * We will want to distinguish between caps structures corresponding to\n> + * raw and non-raw (processed) output images, as this will help inform\n> + * our choice of preferred format.\n> + *\n> + * We identify Bayer as being the principle \"raw\" format here, but note\n> + * that we are considering greyscale (images with one component) to be\n> + * raw too (e.g. a raw monochrome sensor).\n> + */\n> +static bool\n> +gst_libcamera_structure_is_raw_capture(const GstStructure *s)\n> +{\n> +\tif (gst_structure_has_name(s, \"video/x-bayer\"))\n> +\t\treturn true;\n> +\n> +\tif (gst_structure_has_name(s, \"video/x-raw\")) {\n> +\t\tconst gchar *format = gst_structure_get_string(s, \"format\");\n> +\t\tif (!format)\n> +\t\t\treturn false;\n> +\n> +\t\tconst GstVideoFormatInfo *finfo =\n> +\t\t\tgst_video_format_get_info(gst_video_format_from_string(format));\n> +\n> +\t\treturn finfo->n_components == 1;\n> +\t}\n> +\n> +\treturn false;\n> +}\n> +\n> +/*\n> + * Data recorded for each caps structure candidate, used to rank them\n> + * against each other in gst_libcamera_compare_caps_candidates().\n> + */\n> +struct CapsCandidate {\n> +\tguint index;\n> +\tbool is_raw;\n> +\tbool is_fixed;\n> +\tguint delta;\n> +};\n> +\n> +static gint\n> +gst_libcamera_compare_caps_candidates(gconstpointer a, gconstpointer b)\n> +{\n> +\tconst CapsCandidate *ca = static_cast(a);\n> +\tconst CapsCandidate *cb = static_cast(b);\n> +\n> +\t/*\n> +\t * Raw formats are likely to be useful only to applications that\n> +\t * specifically ask for them. Other applications will typically be\n> +\t * unable to handle them and fail, so prefer non-raw candidates.\n> +\t */\n> +\tif (ca->is_raw != cb->is_raw)\n> +\t\treturn ca->is_raw ? 1 : -1;\n> +\n> +\t/* Prefer a reliable fixed value over a range. */\n> +\tif (ca->is_fixed != cb->is_fixed)\n> +\t\treturn ca->is_fixed ? -1 : 1;\n> +\n> +\t/* Otherwise the closest size match wins. */\n> +\tif (ca->delta != cb->delta)\n> +\t\treturn ca->delta < cb->delta ? -1 : 1;\n> +\n> +\treturn 0;\n> +}\n> +\n> +bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> \t\t\t\t\t GstCaps *caps, GstVideoTransferFunction *transfer)\n> {\n> \tGstVideoFormat gst_format = pixel_format_to_gst_format(stream_cfg.pixelFormat);\n> \tguint i;\n> -\tgint best_fixed = -1, best_in_range = -1;\n> \tGstStructure *s;\n> \n> -\t/*\n> -\t * These are delta weight computed from:\n> -\t * ABS(width - stream_cfg.size.width) * ABS(height - stream_cfg.size.height)\n> -\t */\n> -\tguint best_fixed_delta = G_MAXUINT;\n> -\tguint best_in_range_delta = G_MAXUINT;\n> -\n> \t/* First fixate the caps using default configuration value. */\n> \tg_assert(gst_caps_is_writable(caps));\n> \n> -\t/* Lookup the structure for a close match to the stream_cfg.size */\n> +\t/*\n> +\t * Build a candidate for every available caps structure, and insert\n> +\t * it into a list kept sorted by preference as we go. The vector\n> +\t * is constructed at its final size immediately, so it's safe to use\n> +\t * pointers to the elements in it.\n> +\t */\n> +\tstd::vector candidates(gst_caps_get_size(caps));\n> +\tGList *sorted = nullptr;\n\nIt looks to me that `sorted` is unnecessary. In fact, it looks to me that\n`candidates` is unnecessary as well. Now that there is a comparison function,\nit should be a matter of a minimum search, no? Meaning that you only need\nto store the current best? Or am I missing something?\n\nFor example, like this:\n\n\ndiff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp\nindex f0f128880f..95be8a8dcb 100644\n--- a/src/gstreamer/gstlibcamera-utils.cpp\n+++ b/src/gstreamer/gstlibcamera-utils.cpp\n@@ -8,8 +8,9 @@\n \n #include \"gstlibcamera-utils.h\"\n \n+#include \n+#include \n #include \n-#include \n \n #include \n #include \n@@ -474,32 +475,28 @@ struct CapsCandidate {\n \tbool is_raw;\n \tbool is_fixed;\n \tguint delta;\n-};\n-\n-static gint\n-gst_libcamera_compare_caps_candidates(gconstpointer a, gconstpointer b)\n-{\n-\tconst CapsCandidate *ca = static_cast(a);\n-\tconst CapsCandidate *cb = static_cast(b);\n \n-\t/*\n-\t * Raw formats are likely to be useful only to applications that\n-\t * specifically ask for them. Other applications will typically be\n-\t * unable to handle them and fail, so prefer non-raw candidates.\n-\t */\n-\tif (ca->is_raw != cb->is_raw)\n-\t\treturn ca->is_raw ? 1 : -1;\n+\tconstexpr bool operator<(const CapsCandidate &other) const\n+\t{\n+\t\t/*\n+\t\t * Raw formats are likely to be useful only to applications that\n+\t\t * specifically ask for them. Other applications will typically be\n+\t\t * unable to handle them and fail, so prefer non-raw candidates.\n+\t\t */\n+\t\tif (is_raw != other.is_raw)\n+\t\t\treturn !is_raw;\n \n-\t/* Prefer a reliable fixed value over a range. */\n-\tif (ca->is_fixed != cb->is_fixed)\n-\t\treturn ca->is_fixed ? -1 : 1;\n+\t\t/* Prefer a reliable fixed value over a range. */\n+\t\tif (is_fixed != other.is_fixed)\n+\t\t\treturn is_fixed;\n \n-\t/* Otherwise the closest size match wins. */\n-\tif (ca->delta != cb->delta)\n-\t\treturn ca->delta < cb->delta ? -1 : 1;\n+\t\t/* Otherwise the closest size match wins. */\n+\t\tif (delta < other.delta)\n+\t\t\treturn true;\n \n-\treturn 0;\n-}\n+\t\treturn false;\n+\t}\n+};\n \n bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n \t\t\t\t\t GstCaps *caps, GstVideoTransferFunction *transfer)\n@@ -517,8 +514,7 @@ bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n \t * is constructed at its final size immediately, so it's safe to use\n \t * pointers to the elements in it.\n \t */\n-\tstd::vector candidates(gst_caps_get_size(caps));\n-\tGList *sorted = nullptr;\n+\tstd::optional best;\n \n \tfor (i = 0; i < gst_caps_get_size(caps); i++) {\n \t\ts = gst_caps_get_structure(caps, i);\n@@ -536,21 +532,27 @@ bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n \t\t\tgst_structure_get_int(s, \"height\", &height);\n \t\t}\n \n-\t\tguint delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n+\t\tguint delta =\n+\t\t\tguint(std::abs(width - (gint)stream_cfg.size.width))\n+\t\t\t* guint(std::abs(height - (gint)stream_cfg.size.height));\n+\n+\t\tCapsCandidate candidate = {\n+\t\t\t.index = i,\n+\t\t\t.is_raw = gst_libcamera_structure_is_raw_capture(s),\n+\t\t\t.is_fixed = is_fixed,\n+\t\t\t.delta = delta,\n+\t\t};\n \n-\t\tcandidates[i] = { i, gst_libcamera_structure_is_raw_capture(s), is_fixed, delta };\n-\t\tsorted = g_list_insert_sorted(sorted, &candidates[i], gst_libcamera_compare_caps_candidates);\n+\t\tif (!best || candidate < *best)\n+\t\t\tbest = candidate;\n \t}\n \n-\tif (!sorted) {\n+\tif (!best) {\n \t\tGST_WARNING(\"Failed to find a suitable caps structure to configure the stream\");\n \t\treturn false;\n \t}\n \n-\tguint best = static_cast(sorted->data)->index;\n-\tg_list_free(sorted);\n-\n-\ts = gst_caps_get_structure(caps, best);\n+\ts = gst_caps_get_structure(caps, best->index);\n \n \tif (gst_structure_has_name(s, \"video/x-raw\")) {\n \t\tconst gchar *format = gst_video_format_to_string(gst_format);\n\n\n\n\n> +\n> \tfor (i = 0; i < gst_caps_get_size(caps); i++) {\n> \t\ts = gst_caps_get_structure(caps, i);\n> \t\tgint width, height;\n> -\t\tguint delta;\n> +\t\tbool is_fixed = gst_structure_has_field_typed(s, \"width\", G_TYPE_INT) &&\n> +\t\t\t\tgst_structure_has_field_typed(s, \"height\", G_TYPE_INT);\n> \n> -\t\tif (gst_structure_has_field_typed(s, \"width\", G_TYPE_INT) &&\n> -\t\t gst_structure_has_field_typed(s, \"height\", G_TYPE_INT)) {\n> +\t\tif (is_fixed) {\n> \t\t\tgst_structure_get_int(s, \"width\", &width);\n> \t\t\tgst_structure_get_int(s, \"height\", &height);\n> -\n> -\t\t\tdelta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> -\n> -\t\t\tif (delta < best_fixed_delta) {\n> -\t\t\t\tbest_fixed_delta = delta;\n> -\t\t\t\tbest_fixed = i;\n> -\t\t\t}\n> \t\t} else {\n> \t\t\tgst_structure_fixate_field_nearest_int(s, \"width\", stream_cfg.size.width);\n> \t\t\tgst_structure_fixate_field_nearest_int(s, \"height\", stream_cfg.size.height);\n> \t\t\tgst_structure_get_int(s, \"width\", &width);\n> \t\t\tgst_structure_get_int(s, \"height\", &height);\n> +\t\t}\n> \n> -\t\t\tdelta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> +\t\tguint delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> \n> -\t\t\tif (delta < best_in_range_delta) {\n> -\t\t\t\tbest_in_range_delta = delta;\n> -\t\t\t\tbest_in_range = i;\n> -\t\t\t}\n> -\t\t}\n> +\t\tcandidates[i] = { i, gst_libcamera_structure_is_raw_capture(s), is_fixed, delta };\n> +\t\tsorted = g_list_insert_sorted(sorted, &candidates[i], gst_libcamera_compare_caps_candidates);\n> +\t}\n> +\n> +\tif (!sorted) {\n> +\t\tGST_WARNING(\"Failed to find a suitable caps structure to configure the stream\");\n> +\t\treturn false;\n> \t}\n> \n> -\t/* Prefer reliable fixed value over ranges */\n> -\tif (best_fixed >= 0)\n> -\t\ts = gst_caps_get_structure(caps, best_fixed);\n> -\telse\n> -\t\ts = gst_caps_get_structure(caps, best_in_range);\n> +\tguint best = static_cast(sorted->data)->index;\n> +\tg_list_free(sorted);\n> +\n> +\ts = gst_caps_get_structure(caps, best);\n> \n> \tif (gst_structure_has_name(s, \"video/x-raw\")) {\n> \t\tconst gchar *format = gst_video_format_to_string(gst_format);\n> @@ -529,6 +590,8 @@ void gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> \n> \t\tstream_cfg.colorSpace = colorspace_from_colorimetry(colorimetry, transfer);\n> \t}\n> +\n> +\treturn true;\n> }\n> \n> void gst_libcamera_get_framerate_from_caps(GstCaps *caps,\n> diff --git a/src/gstreamer/gstlibcamera-utils.h b/src/gstreamer/gstlibcamera-utils.h\n> index 35df56fb9..5ce0e839c 100644\n> --- a/src/gstreamer/gstlibcamera-utils.h\n> +++ b/src/gstreamer/gstlibcamera-utils.h\n> @@ -18,7 +18,7 @@\n> GstCaps *gst_libcamera_stream_formats_to_caps(const libcamera::StreamFormats &formats);\n> GstCaps *gst_libcamera_stream_configuration_to_caps(const libcamera::StreamConfiguration &stream_cfg,\n> \t\t\t\t\t\t GstVideoTransferFunction transfer);\n> -void gst_libcamera_configure_stream_from_caps(libcamera::StreamConfiguration &stream_cfg,\n> +bool gst_libcamera_configure_stream_from_caps(libcamera::StreamConfiguration &stream_cfg,\n> \t\t\t\t\t GstCaps *caps, GstVideoTransferFunction *transfer);\n> void gst_libcamera_get_framerate_from_caps(GstCaps *caps, GstStructure *element_caps);\n> void gst_libcamera_clamp_and_set_frameduration(libcamera::ControlList &controls,\n> diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp\n> index 9061f9163..66b31ce82 100644\n> --- a/src/gstreamer/gstlibcamerasrc.cpp\n> +++ b/src/gstreamer/gstlibcamerasrc.cpp\n> @@ -605,7 +605,8 @@ gst_libcamera_src_negotiate(GstLibcameraSrc *self)\n> \n> \t\t/* Fixate caps and configure the stream. */\n> \t\tcaps = gst_caps_make_writable(caps);\n> -\t\tgst_libcamera_configure_stream_from_caps(stream_cfg, caps, &transfer[i]);\n> +\t\tif (!gst_libcamera_configure_stream_from_caps(stream_cfg, caps, &transfer[i]))\n> +\t\t\treturn false;\n> \t\tgst_libcamera_get_framerate_from_caps(caps, element_caps);\n> \t}\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com 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d=ideasonboard.com;\n\ts=mail; t=1784553047;\n\tbh=8fpKykI+JyfPRUn1fzJd2wZKu8d1vrXwvnT/Ro8pVFs=;\n\th=Date:Subject:To:References:From:In-Reply-To:From;\n\tb=UWDY8LExiw0YSZWVHOznxCQdI3S+O9YOWyC2Swddp/ObdI10lvWTBIcjnL9SG5ZZ+\n\tvI/ayRhrpy+70yF2qmS1iHdQyePw5MLrn+yEDo4G80lU08lZDMsZHZRgNeQe3Za5vr\n\t7FFYny1sLdStZS5PpTzw5Odh3wVDIQoPuRMK9MJk=","Message-ID":"","Date":"Mon, 20 Jul 2026 15:11:42 +0200","MIME-Version":"1.0","User-Agent":"Mozilla Thunderbird","Subject":"Re: [PATCH v2 1/1] gstreamer: Prefer non-raw (i.e. non-Bayer)\n\tformats in caps negotiation","To":"David Plowman ,\n\tlibcamera-devel@lists.libcamera.org","References":"<20260720115144.4392-1-david.plowman@raspberrypi.com>\n\t<20260720115144.4392-2-david.plowman@raspberrypi.com>","From":"=?utf-8?q?Barnab=C3=A1s_P=C5=91cze?= ","Content-Language":"en-US, hu-HU","In-Reply-To":"<20260720115144.4392-2-david.plowman@raspberrypi.com>","Content-Type":"text/plain; charset=UTF-8; format=flowed","Content-Transfer-Encoding":"8bit","X-BeenThere":"libcamera-devel@lists.libcamera.org","X-Mailman-Version":"2.1.29","Precedence":"list","List-Id":"","List-Unsubscribe":",\n\t","List-Archive":"","List-Post":"","List-Help":"","List-Subscribe":",\n\t","Errors-To":"libcamera-devel-bounces@lists.libcamera.org","Sender":"\"libcamera-devel\" "}},{"id":39796,"web_url":"https://patchwork.libcamera.org/comment/39796/","msgid":"","date":"2026-07-22T12:31:15","subject":"Re: [PATCH v2 1/1] gstreamer: Prefer non-raw (i.e. non-Bayer)\n\tformats in caps negotiation","submitter":{"id":42,"url":"https://patchwork.libcamera.org/api/people/42/","name":"David Plowman","email":"david.plowman@raspberrypi.com"},"content":"Hi Barnabas\n\nThanks for that. Yes, I was copying the v4l2src version a bit too\nclosely, there's no need to do the same thing here. I'll send a\nrevised version.\n\nDavid\n\nOn Mon, 20 Jul 2026 at 14:11, Barnabás Pőcze\n wrote:\n>\n> Hi\n>\n> 2026. 07. 20. 13:10 keltezéssel, David Plowman írta:\n> > Existing code was preferring fixed size outputs over ones with ranges,\n> > resulting in raw output formats being preferred even when applications\n> > (\"cheese\" is one such example) aren't expecting them and subsequently\n> > fail.\n> >\n> > The revised version still prefers fixed size outputs over ones with\n> > ranges, but will prefer non-raw (meaning non-Bayer) formats where\n> > these are available. This still allows applications that explicitly\n> > request raw formats to get them, but other applications will normally\n> > get non-raw formats which they handle better.\n> >\n> > Fixes, for example, \"cheese\" on Raspberry Pi.\n> >\n> > Signed-off-by: David Plowman \n> > ---\n> > src/gstreamer/gstlibcamera-utils.cpp | 125 ++++++++++++++++++++-------\n> > src/gstreamer/gstlibcamera-utils.h | 2 +-\n> > src/gstreamer/gstlibcamerasrc.cpp | 3 +-\n> > 3 files changed, 97 insertions(+), 33 deletions(-)\n> >\n> > diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp\n> > index 6541d478c..f0f128880 100644\n> > --- a/src/gstreamer/gstlibcamera-utils.cpp\n> > +++ b/src/gstreamer/gstlibcamera-utils.cpp\n> > @@ -9,6 +9,7 @@\n> > #include \"gstlibcamera-utils.h\"\n> >\n> > #include \n> > +#include \n> >\n> > #include \n> > #include \n> > @@ -435,61 +436,121 @@ gst_libcamera_stream_configuration_to_caps(const StreamConfiguration &stream_cfg\n> > return caps;\n> > }\n> >\n> > -void gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> > +/*\n> > + * We will want to distinguish between caps structures corresponding to\n> > + * raw and non-raw (processed) output images, as this will help inform\n> > + * our choice of preferred format.\n> > + *\n> > + * We identify Bayer as being the principle \"raw\" format here, but note\n> > + * that we are considering greyscale (images with one component) to be\n> > + * raw too (e.g. a raw monochrome sensor).\n> > + */\n> > +static bool\n> > +gst_libcamera_structure_is_raw_capture(const GstStructure *s)\n> > +{\n> > + if (gst_structure_has_name(s, \"video/x-bayer\"))\n> > + return true;\n> > +\n> > + if (gst_structure_has_name(s, \"video/x-raw\")) {\n> > + const gchar *format = gst_structure_get_string(s, \"format\");\n> > + if (!format)\n> > + return false;\n> > +\n> > + const GstVideoFormatInfo *finfo =\n> > + gst_video_format_get_info(gst_video_format_from_string(format));\n> > +\n> > + return finfo->n_components == 1;\n> > + }\n> > +\n> > + return false;\n> > +}\n> > +\n> > +/*\n> > + * Data recorded for each caps structure candidate, used to rank them\n> > + * against each other in gst_libcamera_compare_caps_candidates().\n> > + */\n> > +struct CapsCandidate {\n> > + guint index;\n> > + bool is_raw;\n> > + bool is_fixed;\n> > + guint delta;\n> > +};\n> > +\n> > +static gint\n> > +gst_libcamera_compare_caps_candidates(gconstpointer a, gconstpointer b)\n> > +{\n> > + const CapsCandidate *ca = static_cast(a);\n> > + const CapsCandidate *cb = static_cast(b);\n> > +\n> > + /*\n> > + * Raw formats are likely to be useful only to applications that\n> > + * specifically ask for them. Other applications will typically be\n> > + * unable to handle them and fail, so prefer non-raw candidates.\n> > + */\n> > + if (ca->is_raw != cb->is_raw)\n> > + return ca->is_raw ? 1 : -1;\n> > +\n> > + /* Prefer a reliable fixed value over a range. */\n> > + if (ca->is_fixed != cb->is_fixed)\n> > + return ca->is_fixed ? -1 : 1;\n> > +\n> > + /* Otherwise the closest size match wins. */\n> > + if (ca->delta != cb->delta)\n> > + return ca->delta < cb->delta ? -1 : 1;\n> > +\n> > + return 0;\n> > +}\n> > +\n> > +bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> > GstCaps *caps, GstVideoTransferFunction *transfer)\n> > {\n> > GstVideoFormat gst_format = pixel_format_to_gst_format(stream_cfg.pixelFormat);\n> > guint i;\n> > - gint best_fixed = -1, best_in_range = -1;\n> > GstStructure *s;\n> >\n> > - /*\n> > - * These are delta weight computed from:\n> > - * ABS(width - stream_cfg.size.width) * ABS(height - stream_cfg.size.height)\n> > - */\n> > - guint best_fixed_delta = G_MAXUINT;\n> > - guint best_in_range_delta = G_MAXUINT;\n> > -\n> > /* First fixate the caps using default configuration value. */\n> > g_assert(gst_caps_is_writable(caps));\n> >\n> > - /* Lookup the structure for a close match to the stream_cfg.size */\n> > + /*\n> > + * Build a candidate for every available caps structure, and insert\n> > + * it into a list kept sorted by preference as we go. The vector\n> > + * is constructed at its final size immediately, so it's safe to use\n> > + * pointers to the elements in it.\n> > + */\n> > + std::vector candidates(gst_caps_get_size(caps));\n> > + GList *sorted = nullptr;\n>\n> It looks to me that `sorted` is unnecessary. In fact, it looks to me that\n> `candidates` is unnecessary as well. Now that there is a comparison function,\n> it should be a matter of a minimum search, no? Meaning that you only need\n> to store the current best? Or am I missing something?\n>\n> For example, like this:\n>\n>\n> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp\n> index f0f128880f..95be8a8dcb 100644\n> --- a/src/gstreamer/gstlibcamera-utils.cpp\n> +++ b/src/gstreamer/gstlibcamera-utils.cpp\n> @@ -8,8 +8,9 @@\n>\n> #include \"gstlibcamera-utils.h\"\n>\n> +#include \n> +#include \n> #include \n> -#include \n>\n> #include \n> #include \n> @@ -474,32 +475,28 @@ struct CapsCandidate {\n> bool is_raw;\n> bool is_fixed;\n> guint delta;\n> -};\n> -\n> -static gint\n> -gst_libcamera_compare_caps_candidates(gconstpointer a, gconstpointer b)\n> -{\n> - const CapsCandidate *ca = static_cast(a);\n> - const CapsCandidate *cb = static_cast(b);\n>\n> - /*\n> - * Raw formats are likely to be useful only to applications that\n> - * specifically ask for them. Other applications will typically be\n> - * unable to handle them and fail, so prefer non-raw candidates.\n> - */\n> - if (ca->is_raw != cb->is_raw)\n> - return ca->is_raw ? 1 : -1;\n> + constexpr bool operator<(const CapsCandidate &other) const\n> + {\n> + /*\n> + * Raw formats are likely to be useful only to applications that\n> + * specifically ask for them. Other applications will typically be\n> + * unable to handle them and fail, so prefer non-raw candidates.\n> + */\n> + if (is_raw != other.is_raw)\n> + return !is_raw;\n>\n> - /* Prefer a reliable fixed value over a range. */\n> - if (ca->is_fixed != cb->is_fixed)\n> - return ca->is_fixed ? -1 : 1;\n> + /* Prefer a reliable fixed value over a range. */\n> + if (is_fixed != other.is_fixed)\n> + return is_fixed;\n>\n> - /* Otherwise the closest size match wins. */\n> - if (ca->delta != cb->delta)\n> - return ca->delta < cb->delta ? -1 : 1;\n> + /* Otherwise the closest size match wins. */\n> + if (delta < other.delta)\n> + return true;\n>\n> - return 0;\n> -}\n> + return false;\n> + }\n> +};\n>\n> bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> GstCaps *caps, GstVideoTransferFunction *transfer)\n> @@ -517,8 +514,7 @@ bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> * is constructed at its final size immediately, so it's safe to use\n> * pointers to the elements in it.\n> */\n> - std::vector candidates(gst_caps_get_size(caps));\n> - GList *sorted = nullptr;\n> + std::optional best;\n>\n> for (i = 0; i < gst_caps_get_size(caps); i++) {\n> s = gst_caps_get_structure(caps, i);\n> @@ -536,21 +532,27 @@ bool gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> gst_structure_get_int(s, \"height\", &height);\n> }\n>\n> - guint delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> + guint delta =\n> + guint(std::abs(width - (gint)stream_cfg.size.width))\n> + * guint(std::abs(height - (gint)stream_cfg.size.height));\n> +\n> + CapsCandidate candidate = {\n> + .index = i,\n> + .is_raw = gst_libcamera_structure_is_raw_capture(s),\n> + .is_fixed = is_fixed,\n> + .delta = delta,\n> + };\n>\n> - candidates[i] = { i, gst_libcamera_structure_is_raw_capture(s), is_fixed, delta };\n> - sorted = g_list_insert_sorted(sorted, &candidates[i], gst_libcamera_compare_caps_candidates);\n> + if (!best || candidate < *best)\n> + best = candidate;\n> }\n>\n> - if (!sorted) {\n> + if (!best) {\n> GST_WARNING(\"Failed to find a suitable caps structure to configure the stream\");\n> return false;\n> }\n>\n> - guint best = static_cast(sorted->data)->index;\n> - g_list_free(sorted);\n> -\n> - s = gst_caps_get_structure(caps, best);\n> + s = gst_caps_get_structure(caps, best->index);\n>\n> if (gst_structure_has_name(s, \"video/x-raw\")) {\n> const gchar *format = gst_video_format_to_string(gst_format);\n>\n>\n>\n>\n> > +\n> > for (i = 0; i < gst_caps_get_size(caps); i++) {\n> > s = gst_caps_get_structure(caps, i);\n> > gint width, height;\n> > - guint delta;\n> > + bool is_fixed = gst_structure_has_field_typed(s, \"width\", G_TYPE_INT) &&\n> > + gst_structure_has_field_typed(s, \"height\", G_TYPE_INT);\n> >\n> > - if (gst_structure_has_field_typed(s, \"width\", G_TYPE_INT) &&\n> > - gst_structure_has_field_typed(s, \"height\", G_TYPE_INT)) {\n> > + if (is_fixed) {\n> > gst_structure_get_int(s, \"width\", &width);\n> > gst_structure_get_int(s, \"height\", &height);\n> > -\n> > - delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> > -\n> > - if (delta < best_fixed_delta) {\n> > - best_fixed_delta = delta;\n> > - best_fixed = i;\n> > - }\n> > } else {\n> > gst_structure_fixate_field_nearest_int(s, \"width\", stream_cfg.size.width);\n> > gst_structure_fixate_field_nearest_int(s, \"height\", stream_cfg.size.height);\n> > gst_structure_get_int(s, \"width\", &width);\n> > gst_structure_get_int(s, \"height\", &height);\n> > + }\n> >\n> > - delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> > + guint delta = ABS(width - (gint)stream_cfg.size.width) * ABS(height - (gint)stream_cfg.size.height);\n> >\n> > - if (delta < best_in_range_delta) {\n> > - best_in_range_delta = delta;\n> > - best_in_range = i;\n> > - }\n> > - }\n> > + candidates[i] = { i, gst_libcamera_structure_is_raw_capture(s), is_fixed, delta };\n> > + sorted = g_list_insert_sorted(sorted, &candidates[i], gst_libcamera_compare_caps_candidates);\n> > + }\n> > +\n> > + if (!sorted) {\n> > + GST_WARNING(\"Failed to find a suitable caps structure to configure the stream\");\n> > + return false;\n> > }\n> >\n> > - /* Prefer reliable fixed value over ranges */\n> > - if (best_fixed >= 0)\n> > - s = gst_caps_get_structure(caps, best_fixed);\n> > - else\n> > - s = gst_caps_get_structure(caps, best_in_range);\n> > + guint best = static_cast(sorted->data)->index;\n> > + g_list_free(sorted);\n> > +\n> > + s = gst_caps_get_structure(caps, best);\n> >\n> > if (gst_structure_has_name(s, \"video/x-raw\")) {\n> > const gchar *format = gst_video_format_to_string(gst_format);\n> > @@ -529,6 +590,8 @@ void gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,\n> >\n> > stream_cfg.colorSpace = colorspace_from_colorimetry(colorimetry, transfer);\n> > }\n> > +\n> > + return true;\n> > }\n> >\n> > void gst_libcamera_get_framerate_from_caps(GstCaps *caps,\n> > diff --git a/src/gstreamer/gstlibcamera-utils.h b/src/gstreamer/gstlibcamera-utils.h\n> > index 35df56fb9..5ce0e839c 100644\n> > --- a/src/gstreamer/gstlibcamera-utils.h\n> > +++ b/src/gstreamer/gstlibcamera-utils.h\n> > @@ -18,7 +18,7 @@\n> > GstCaps *gst_libcamera_stream_formats_to_caps(const libcamera::StreamFormats &formats);\n> > GstCaps *gst_libcamera_stream_configuration_to_caps(const libcamera::StreamConfiguration &stream_cfg,\n> > GstVideoTransferFunction transfer);\n> > -void gst_libcamera_configure_stream_from_caps(libcamera::StreamConfiguration &stream_cfg,\n> > +bool gst_libcamera_configure_stream_from_caps(libcamera::StreamConfiguration &stream_cfg,\n> > GstCaps *caps, GstVideoTransferFunction *transfer);\n> > void gst_libcamera_get_framerate_from_caps(GstCaps *caps, GstStructure *element_caps);\n> > void gst_libcamera_clamp_and_set_frameduration(libcamera::ControlList &controls,\n> > diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp\n> > index 9061f9163..66b31ce82 100644\n> > --- a/src/gstreamer/gstlibcamerasrc.cpp\n> > +++ b/src/gstreamer/gstlibcamerasrc.cpp\n> > @@ -605,7 +605,8 @@ gst_libcamera_src_negotiate(GstLibcameraSrc *self)\n> >\n> > /* Fixate caps and configure the stream. */\n> > caps = gst_caps_make_writable(caps);\n> > - gst_libcamera_configure_stream_from_caps(stream_cfg, caps, &transfer[i]);\n> > + if (!gst_libcamera_configure_stream_from_caps(stream_cfg, caps, &transfer[i]))\n> > + return false;\n> > gst_libcamera_get_framerate_from_caps(caps, element_caps);\n> > }\n> >\n>","headers":{"Return-Path":"","X-Original-To":"parsemail@patchwork.libcamera.org","Delivered-To":"parsemail@patchwork.libcamera.org","Received":["from lancelot.ideasonboard.com (lancelot.ideasonboard.com\n\t[92.243.16.209])\n\tby patchwork.libcamera.org (Postfix) with ESMTPS id 0B24CBDE17\n\tfor ;\n\tWed, 22 Jul 2026 12:31:30 +0000 (UTC)","from lancelot.ideasonboard.com (localhost [IPv6:::1])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTP id D374667EA3;\n\tWed, 22 Jul 2026 14:31:28 +0200 (CEST)","from mail-ed1-x533.google.com (mail-ed1-x533.google.com\n\t[IPv6:2a00:1450:4864:20::533])\n\tby lancelot.ideasonboard.com (Postfix) with ESMTPS id 44EA167E8A\n\tfor ;\n\tWed, 22 Jul 2026 14:31:27 +0200 (CEST)","by mail-ed1-x533.google.com with SMTP id\n\t4fb4d7f45d1cf-698beff7178so12306252a12.3\n\tfor ;\n\tWed, 22 Jul 2026 05:31:27 -0700 (PDT)"],"Authentication-Results":"lancelot.ideasonboard.com; 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