y4m: share common code among encoder and decoder

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8719>

subprojects/gst-plugins-good/gst/y4m/gsty4mdec.c

@@ -37,6 +37,7 @@
 #include <string.h>
 
 #include "gsty4mdec.h"
+#include "gsty4mformat.h"
 
 #define MAX_SIZE 32768
 
@@ -387,6 +388,7 @@ gst_y4m_dec_parse_header (GstY4mDec * y4mdec, char *header)
   gulong par_n = 0, par_d = 0;
   gulong width = 0, height = 0;
   GstVideoFormat format = GST_VIDEO_FORMAT_I420;
+  GstVideoInterlaceMode interlace_mode;
 
   if (memcmp (header, "YUV4MPEG2 ", 10) != 0) {
     GST_ERROR_OBJECT (y4mdec, "y4m start code not found");
@@ -458,59 +460,15 @@ gst_y4m_dec_parse_header (GstY4mDec * y4mdec, char *header)
     return FALSE;
   }
 
-  gst_video_info_init (&y4mdec->info);
-  gst_video_info_set_format (&y4mdec->out_info, format, width, height);
-  y4mdec->info = y4mdec->out_info;
-
-  switch (y4mdec->info.finfo->format) {
-    case GST_VIDEO_FORMAT_I420:
-      y4mdec->info.offset[0] = 0;
-      y4mdec->info.stride[0] = width;
-      y4mdec->info.offset[1] = y4mdec->info.stride[0] * height;
-      y4mdec->info.stride[1] = GST_ROUND_UP_2 (width) / 2;
-      y4mdec->info.offset[2] =
-          y4mdec->info.offset[1] +
-          y4mdec->info.stride[1] * (GST_ROUND_UP_2 (height) / 2);
-      y4mdec->info.stride[2] = GST_ROUND_UP_2 (width) / 2;
-      y4mdec->info.size =
-          y4mdec->info.offset[2] +
-          y4mdec->info.stride[2] * (GST_ROUND_UP_2 (height) / 2);
-      break;
-    case GST_VIDEO_FORMAT_Y42B:
-      y4mdec->info.offset[0] = 0;
-      y4mdec->info.stride[0] = width;
-      y4mdec->info.offset[1] = y4mdec->info.stride[0] * height;
-      y4mdec->info.stride[1] = GST_ROUND_UP_2 (width) / 2;
-      y4mdec->info.offset[2] =
-          y4mdec->info.offset[1] + y4mdec->info.stride[1] * height;
-      y4mdec->info.stride[2] = GST_ROUND_UP_2 (width) / 2;
-      y4mdec->info.size =
-          y4mdec->info.offset[2] + y4mdec->info.stride[2] * height;
-      break;
-    case GST_VIDEO_FORMAT_Y444:
-      y4mdec->info.offset[0] = 0;
-      y4mdec->info.stride[0] = width;
-      y4mdec->info.offset[1] = y4mdec->info.stride[0] * height;
-      y4mdec->info.stride[1] = width;
-      y4mdec->info.offset[2] =
-          y4mdec->info.offset[1] + y4mdec->info.stride[1] * height;
-      y4mdec->info.stride[2] = width;
-      y4mdec->info.size =
-          y4mdec->info.offset[2] + y4mdec->info.stride[2] * height;
-      break;
-    default:
-      break;
-  }
-
   switch (interlaced_char) {
     case 0:
     case '?':
     case 'p':
-      y4mdec->info.interlace_mode = GST_VIDEO_INTERLACE_MODE_PROGRESSIVE;
+      interlace_mode = GST_VIDEO_INTERLACE_MODE_PROGRESSIVE;
       break;
     case 't':
     case 'b':
-      y4mdec->info.interlace_mode = GST_VIDEO_INTERLACE_MODE_INTERLEAVED;
+      interlace_mode = GST_VIDEO_INTERLACE_MODE_INTERLEAVED;
       break;
     default:
       GST_ERROR_OBJECT (y4mdec, "Unknown interlaced char '%c'",
@@ -528,10 +486,17 @@ gst_y4m_dec_parse_header (GstY4mDec * y4mdec, char *header)
   if (par_d == 0)
     par_d = 1;
 
-  y4mdec->info.fps_n = fps_n;
+  gst_video_info_set_interlaced_format (&y4mdec->out_info, format,
-  y4mdec->info.fps_d = fps_d;
+      interlace_mode, width, height);
-  y4mdec->info.par_n = par_n;
+
-  y4mdec->info.par_d = par_d;
+  GST_VIDEO_INFO_FPS_N (&y4mdec->out_info) = fps_n;
+  GST_VIDEO_INFO_FPS_D (&y4mdec->out_info) = fps_d;
+  GST_VIDEO_INFO_PAR_N (&y4mdec->out_info) = par_n;
+  GST_VIDEO_INFO_PAR_D (&y4mdec->out_info) = par_d;
+
+  if (!gst_y4m_video_unpadded_info (&y4mdec->info, &y4mdec->out_info))
+    return FALSE;
+
 
   return TRUE;
 }

subprojects/gst-plugins-good/gst/y4m/gsty4menc.c

@@ -43,6 +43,7 @@
 #include <string.h>
 
 #include "gsty4menc.h"
+#include "gsty4mformat.h"
 
 /* Filter signals and args */
 enum
@@ -139,69 +140,30 @@ gst_y4m_encode_set_format (GstVideoEncoder * encoder,
   GstY4mEncode *y4menc;
   GstVideoInfo *info, out_info;
   GstVideoCodecState *output_state;
-  gint width, height;
-  GstVideoFormat format;
-  gsize cr_h;
 
   y4menc = GST_Y4M_ENCODE (encoder);
   info = &state->info;
 
-  format = GST_VIDEO_INFO_FORMAT (info);
+  switch (GST_VIDEO_INFO_FORMAT (info)) {
-  width = GST_VIDEO_INFO_WIDTH (info);
-  height = GST_VIDEO_INFO_HEIGHT (info);
-
-  gst_video_info_set_format (&out_info, format, width, height);
-
-  switch (format) {
     case GST_VIDEO_FORMAT_I420:
       y4menc->colorspace = "420";
-      out_info.stride[0] = width;
-      out_info.stride[1] = GST_ROUND_UP_2 (width) / 2;
-      out_info.stride[2] = out_info.stride[1];
-      out_info.offset[0] = 0;
-      out_info.offset[1] = out_info.stride[0] * height;
-      cr_h = GST_ROUND_UP_2 (height) / 2;
-      if (GST_VIDEO_INFO_IS_INTERLACED (info))
-        cr_h = GST_ROUND_UP_2 (height);
-      out_info.offset[2] = out_info.offset[1] + out_info.stride[1] * cr_h;
-      out_info.size = out_info.offset[2] + out_info.stride[2] * cr_h;
       break;
     case GST_VIDEO_FORMAT_Y42B:
       y4menc->colorspace = "422";
-      out_info.stride[0] = width;
-      out_info.stride[1] = GST_ROUND_UP_2 (width) / 2;
-      out_info.stride[2] = out_info.stride[1];
-      out_info.offset[0] = 0;
-      out_info.offset[1] = out_info.stride[0] * height;
-      out_info.offset[2] = out_info.offset[1] + out_info.stride[1] * height;
-      /* simplification of ROUNDUP4(w)*h + 2*(ROUNDUP8(w)/2)*h */
-      out_info.size = out_info.offset[2] + out_info.stride[2] * height;
       break;
     case GST_VIDEO_FORMAT_Y41B:
       y4menc->colorspace = "411";
-      out_info.stride[0] = width;
-      out_info.stride[1] = GST_ROUND_UP_2 (width) / 4;
-      out_info.stride[2] = out_info.stride[1];
-      out_info.offset[0] = 0;
-      out_info.offset[1] = out_info.stride[0] * height;
-      out_info.offset[2] = out_info.offset[1] + out_info.stride[1] * height;
-      /* simplification of ROUNDUP4(w)*h + 2*((ROUNDUP16(w)/4)*h */
-      out_info.size = (width + (GST_ROUND_UP_2 (width) / 2)) * height;
       break;
     case GST_VIDEO_FORMAT_Y444:
       y4menc->colorspace = "444";
-      out_info.stride[0] = width;
-      out_info.stride[1] = out_info.stride[0];
-      out_info.stride[2] = out_info.stride[0];
-      out_info.offset[0] = 0;
-      out_info.offset[1] = out_info.stride[0] * height;
-      out_info.offset[2] = out_info.offset[1] * 2;
-      out_info.size = out_info.stride[0] * height * 3;
       break;
     default:
       goto invalid_format;
   }
 
+  if (!gst_y4m_video_unpadded_info (&out_info, info))
+    goto invalid_format;
+
   y4menc->info = *info;
   y4menc->out_info = out_info;
   y4menc->padded = !gst_video_info_is_equal (info, &out_info);

subprojects/gst-plugins-good/gst/y4m/gsty4mformat.c

@@ -0,0 +1,93 @@
+/* GStreamer
+ * Copyright (C) 2025 Igalia, S.L.
+ *               Author: Victor Jaquez <vjaquez@igalia.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gsty4mformat.h"
+
+gboolean
+gst_y4m_video_unpadded_info (GstVideoInfo * y4m_info,
+    const GstVideoInfo * vinfo)
+{
+  g_return_val_if_fail (y4m_info && vinfo, FALSE);
+
+  gsize cr_h;
+  guint width, height;
+  GstVideoFormat format;
+  GstVideoInfo out_info;
+
+  format = GST_VIDEO_INFO_FORMAT (vinfo);
+  width = GST_VIDEO_INFO_WIDTH (vinfo);
+  height = GST_VIDEO_INFO_HEIGHT (vinfo);
+
+  out_info = *vinfo;
+
+  switch (format) {
+    case GST_VIDEO_FORMAT_I420:
+      out_info.stride[0] = width;
+      out_info.stride[1] = GST_ROUND_UP_2 (width) / 2;
+      out_info.stride[2] = out_info.stride[1];
+      out_info.offset[0] = 0;
+      out_info.offset[1] = out_info.stride[0] * height;
+      cr_h = GST_ROUND_UP_2 (height) / 2;
+      if (GST_VIDEO_INFO_IS_INTERLACED (vinfo))
+        cr_h = GST_ROUND_UP_2 (height);
+      out_info.offset[2] = out_info.offset[1] + out_info.stride[1] * cr_h;
+      out_info.size = out_info.offset[2] + out_info.stride[2] * cr_h;
+      break;
+    case GST_VIDEO_FORMAT_Y42B:
+      out_info.stride[0] = width;
+      out_info.stride[1] = GST_ROUND_UP_2 (width) / 2;
+      out_info.stride[2] = out_info.stride[1];
+      out_info.offset[0] = 0;
+      out_info.offset[1] = out_info.stride[0] * height;
+      out_info.offset[2] = out_info.offset[1] + out_info.stride[1] * height;
+      /* simplification of ROUNDUP4(w)*h + 2*(ROUNDUP8(w)/2)*h */
+      out_info.size = out_info.offset[2] + out_info.stride[2] * height;
+      break;
+    case GST_VIDEO_FORMAT_Y41B:
+      out_info.stride[0] = width;
+      out_info.stride[1] = GST_ROUND_UP_2 (width) / 4;
+      out_info.stride[2] = out_info.stride[1];
+      out_info.offset[0] = 0;
+      out_info.offset[1] = out_info.stride[0] * height;
+      out_info.offset[2] = out_info.offset[1] + out_info.stride[1] * height;
+      /* simplification of ROUNDUP4(w)*h + 2*((ROUNDUP16(w)/4)*h */
+      out_info.size = (width + (GST_ROUND_UP_2 (width) / 2)) * height;
+      break;
+    case GST_VIDEO_FORMAT_Y444:
+      out_info.stride[0] = width;
+      out_info.stride[1] = out_info.stride[0];
+      out_info.stride[2] = out_info.stride[0];
+      out_info.offset[0] = 0;
+      out_info.offset[1] = out_info.stride[0] * height;
+      out_info.offset[2] = out_info.offset[1] * 2;
+      out_info.size = out_info.stride[0] * height * 3;
+      break;
+    default:
+      GST_FIXME ("%s is not supported", gst_video_format_to_string (format));
+  }
+
+  *y4m_info = out_info;
+
+  return TRUE;
+}

subprojects/gst-plugins-good/gst/y4m/gsty4mformat.h

@@ -0,0 +1,27 @@
+/* GStreamer
+ * Copyright (C) 2025 Igalia, S.L.
+ *               Author: Victor Jaquez <vjaquez@igalia.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Library General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Library General Public License for more details.
+ *
+ * You should have received a copy of the GNU Library General Public
+ * License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 51 Franklin St, Fifth Floor,
+ * Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+#include <gst/gst.h>
+#include <gst/video/video.h>
+
+gboolean              gst_y4m_video_unpadded_info (GstVideoInfo * y4m_info,
+                                                   const GstVideoInfo * vinfo);

subprojects/gst-plugins-good/gst/y4m/meson.build

@@ -1,5 +1,6 @@
 y4m_sources = [
   'plugin.c',
+  'gsty4mformat.c',
   'gsty4menc.c',
   'gsty4mdec.c'
 ]