[FFmpeg-devel] [PATCH 10/23] lavc/movtextdec: allow setting subtitle frame dimensions

John Stebbins jstebbins at jetheaddev.com
Mon Apr 6 20:52:05 EEST 2020


Font sizes are relative to the subtitle frame dimensions. If the
expected frame dimensions are not known, the font sizes will most
likely be incorrect.
---
 libavcodec/ass.c        | 30 +++++++++++++++++++++++-------
 libavcodec/ass.h        | 28 ++++++++++++++++++++++++++++
 libavcodec/movtextdec.c | 30 +++++++++++++++++++++++++++++-
 3 files changed, 80 insertions(+), 8 deletions(-)

diff --git a/libavcodec/ass.c b/libavcodec/ass.c
index a51673fb4e..7c26e3fd6d 100644
--- a/libavcodec/ass.c
+++ b/libavcodec/ass.c
@@ -26,11 +26,13 @@
 #include "libavutil/bprint.h"
 #include "libavutil/common.h"
 
-int ff_ass_subtitle_header(AVCodecContext *avctx,
-                           const char *font, int font_size,
-                           int color, int back_color,
-                           int bold, int italic, int underline,
-                           int border_style, int alignment)
+int ff_ass_subtitle_header_full(AVCodecContext *avctx,
+                                int play_res_x, int play_res_y,
+                                const char *font, int font_size,
+                                int primary_color, int secondary_color,
+                                int outline_color, int back_color,
+                                int bold, int italic, int underline,
+                                int border_style, int alignment)
 {
     avctx->subtitle_header = av_asprintf(
              "[Script Info]\r\n"
@@ -67,8 +69,8 @@ int ff_ass_subtitle_header(AVCodecContext *avctx,
              "[Events]\r\n"
              "Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text\r\n",
              !(avctx->flags & AV_CODEC_FLAG_BITEXACT) ? AV_STRINGIFY(LIBAVCODEC_VERSION) : "",
-             ASS_DEFAULT_PLAYRESX, ASS_DEFAULT_PLAYRESY,
-             font, font_size, color, color, back_color, back_color,
+             play_res_x, play_res_y, font, font_size,
+             primary_color, secondary_color, outline_color, back_color,
              -bold, -italic, -underline, border_style, alignment);
 
     if (!avctx->subtitle_header)
@@ -77,6 +79,20 @@ int ff_ass_subtitle_header(AVCodecContext *avctx,
     return 0;
 }
 
+int ff_ass_subtitle_header(AVCodecContext *avctx,
+                           const char *font, int font_size,
+                           int color, int back_color,
+                           int bold, int italic, int underline,
+                           int border_style, int alignment)
+{
+    return ff_ass_subtitle_header_full(avctx,
+                               ASS_DEFAULT_PLAYRESX, ASS_DEFAULT_PLAYRESY,
+                               font, font_size, color, color,
+                               back_color, back_color,
+                               bold, italic, underline,
+                               border_style, alignment);
+}
+
 int ff_ass_subtitle_header_default(AVCodecContext *avctx)
 {
     return ff_ass_subtitle_header(avctx, ASS_DEFAULT_FONT,
diff --git a/libavcodec/ass.h b/libavcodec/ass.h
index 314b43b686..2c260e4e78 100644
--- a/libavcodec/ass.h
+++ b/libavcodec/ass.h
@@ -47,6 +47,34 @@ typedef struct FFASSDecoderContext {
     int readorder;
 } FFASSDecoderContext;
 
+/**
+ * Generate a suitable AVCodecContext.subtitle_header for SUBTITLE_ASS.
+ * Can specify all fields explicitly
+ *
+ * @param avctx pointer to the AVCodecContext
+ * @param play_res_x subtitle frame width
+ * @param play_res_y subtitle frame height
+ * @param font name of the default font face to use
+ * @param font_size default font size to use
+ * @param primary_color default text color to use (ABGR)
+ * @param secondary_color default secondary text color to use (ABGR)
+ * @param outline_color default outline color to use (ABGR)
+ * @param back_color default background color to use (ABGR)
+ * @param bold 1 for bold text, 0 for normal text
+ * @param italic 1 for italic text, 0 for normal text
+ * @param underline 1 for underline text, 0 for normal text
+ * @param border_style 1 for outline, 3 for opaque box
+ * @param alignment position of the text (left, center, top...), defined after
+ *                  the layout of the numpad (1-3 sub, 4-6 mid, 7-9 top)
+ * @return >= 0 on success otherwise an error code <0
+ */
+int ff_ass_subtitle_header_full(AVCodecContext *avctx,
+                                int play_res_x, int play_res_y,
+                                const char *font, int font_size,
+                                int primary_color, int secondary_color,
+                                int outline_color, int back_color,
+                                int bold, int italic, int underline,
+                                int border_style, int alignment);
 /**
  * Generate a suitable AVCodecContext.subtitle_header for SUBTITLE_ASS.
  *
diff --git a/libavcodec/movtextdec.c b/libavcodec/movtextdec.c
index f3a504b47b..4b4da5e0d9 100644
--- a/libavcodec/movtextdec.c
+++ b/libavcodec/movtextdec.c
@@ -21,6 +21,7 @@
 
 #include "avcodec.h"
 #include "ass.h"
+#include "libavutil/opt.h"
 #include "libavutil/avstring.h"
 #include "libavutil/common.h"
 #include "libavutil/bprint.h"
@@ -96,6 +97,7 @@ typedef struct {
 } TextWrapBox;
 
 typedef struct {
+    AVClass *class;
     StyleBox **s;
     StyleBox *s_temp;
     HighlightBox h;
@@ -110,6 +112,8 @@ typedef struct {
     int size_var;
     int count_s, count_f;
     int readorder;
+    int frame_width;
+    int frame_height;
 } MovTextContext;
 
 typedef struct {
@@ -481,9 +485,17 @@ static int mov_text_init(AVCodecContext *avctx) {
     MovTextContext *m = avctx->priv_data;
     ret = mov_text_tx3g(avctx, m);
     if (ret == 0) {
-        return ff_ass_subtitle_header(avctx, m->d.font, m->d.fontsize,
+        if (!m->frame_width || !m->frame_height) {
+            m->frame_width = ASS_DEFAULT_PLAYRESX;
+            m->frame_height = ASS_DEFAULT_PLAYRESY;
+        }
+        return ff_ass_subtitle_header_full(avctx,
+                    m->frame_width, m->frame_height,
+                    m->d.font, m->d.fontsize,
+                    (255 - m->d.alpha) << 24 | RGB_TO_BGR(m->d.color),
                     (255 - m->d.alpha) << 24 | RGB_TO_BGR(m->d.color),
                     (255 - m->d.back_alpha) << 24 | RGB_TO_BGR(m->d.back_color),
+                    (255 - m->d.back_alpha) << 24 | RGB_TO_BGR(m->d.back_color),
                     m->d.bold, m->d.italic, m->d.underline,
                     ASS_DEFAULT_BORDERSTYLE, m->d.alignment);
     } else
@@ -601,12 +613,28 @@ static void mov_text_flush(AVCodecContext *avctx)
         m->readorder = 0;
 }
 
+#define OFFSET(x) offsetof(MovTextContext, x)
+#define FLAGS AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_SUBTITLE_PARAM
+static const AVOption options[] = {
+    { "width", "Frame width, usually video width", OFFSET(frame_width), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS },
+    { "height", "Frame height, usually video height", OFFSET(frame_height), AV_OPT_TYPE_INT, {.i64=0}, 0, INT_MAX, FLAGS },
+    { NULL },
+};
+
+static const AVClass mov_text_decoder_class = {
+    .class_name = "MOV text decoder",
+    .item_name  = av_default_item_name,
+    .option     = options,
+    .version    = LIBAVUTIL_VERSION_INT,
+};
+
 AVCodec ff_movtext_decoder = {
     .name         = "mov_text",
     .long_name    = NULL_IF_CONFIG_SMALL("3GPP Timed Text subtitle"),
     .type         = AVMEDIA_TYPE_SUBTITLE,
     .id           = AV_CODEC_ID_MOV_TEXT,
     .priv_data_size = sizeof(MovTextContext),
+    .priv_class   = &mov_text_decoder_class,
     .init         = mov_text_init,
     .decode       = mov_text_decode_frame,
     .close        = mov_text_decode_close,
-- 
2.25.1



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