[FFmpeg-devel] [PATCH]Basic XSUB encoder (take 5)

Reimar Döffinger Reimar.Doeffinger
Sat May 23 17:22:44 CEST 2009


On Sun, Feb 08, 2009 at 03:20:21AM +0100, Michael Niedermayer wrote:
> On Sat, Feb 07, 2009 at 03:33:12PM +0100, Bj?rn Axelsson wrote:
> > [...]
> > 
> > > > Index: libavformat/avienc.c
> > > > ===================================================================
> > > > --- libavformat/avienc.c.orig	2009-02-05 21:17:03.000000000 +0100
> > > > +++ libavformat/avienc.c	2009-02-05 21:17:36.000000000 +0100
> > > > @@ -82,6 +82,9 @@
> > > >      if (type == CODEC_TYPE_VIDEO) {
> > > >          tag[2] = 'd';
> > > >          tag[3] = 'c';
> > > > +    } else if (type == CODEC_TYPE_SUBTITLE) {
> > > > +        tag[2] = 's';
> > > > +        tag[3] = 'b';
> > > >      } else {
> > > >          tag[2] = 'w';
> > > >          tag[3] = 'b';
> > > > @@ -213,8 +216,10 @@
> > > >          case CODEC_TYPE_AUDIO: put_tag(pb, "auds"); break;
> > > >  //        case CODEC_TYPE_TEXT : put_tag(pb, "txts"); break;
> > > >          case CODEC_TYPE_DATA : put_tag(pb, "dats"); break;
> > > > +        case CODEC_TYPE_SUBTITLE: put_tag(pb, "vids"); break;
> > > >          }
> > > > -        if(stream->codec_type == CODEC_TYPE_VIDEO)
> > >
> > > > +        if(stream->codec_type == CODEC_TYPE_VIDEO
> > > > +                || stream->codec_type == CODEC_TYPE_SUBTITLE)
> > > >              put_le32(pb, stream->codec_tag);
> > > >          else
> > > >              put_le32(pb, 1);
> > >
> > > this may be wrong as we have a ('t', 'x', 't', 's') in avidec as well so
> > > not all might be vids
> > 
> > At the moment "txts" is handled as CODEC_TYPE_DATA in avidec, so there's
> > no risk for immediate breakage. I think...
> > 
> > My knowledge about the avi (de)muxer is very limited, but maybe I could
> > add CODEC_CAP_SUBTITLE_{BITMAP | TEXT | ASS} and do something like
> > 
> > case CODEC_TYPE_SUBTITLE:
> >     if(stream->capabilities & CODEC_CAP_SUBTITLE_BITMAP)
> >        put_tag(pb, "vids");
> >     else
> >        put_tag(pb, "txts");
> >     break;
> > 
> > and something similar with the header later on?
> 
> this might indeed be approximately correct

Haven't done anything on the muxer code part, but I fixed the trivial
stuff pointed out here and one or two more simplifications and updated
to SVN.
-------------- next part --------------
Index: ffmpeg.c
===================================================================
--- ffmpeg.c	(revision 18911)
+++ ffmpeg.c	(working copy)
@@ -818,6 +818,7 @@
         nb = 1;
 
     for(i = 0; i < nb; i++) {
+        sub->pts = av_rescale_q(pts, ist->st->time_base, AV_TIME_BASE_Q);
         subtitle_out_size = avcodec_encode_subtitle(enc, subtitle_out,
                                                     subtitle_out_max_size, sub);
 
Index: Changelog
===================================================================
--- Changelog	(revision 18911)
+++ Changelog	(working copy)
@@ -20,6 +20,7 @@
 - V210 decoder and encoder
 - remaining GPL parts in AC-3 decoder converted to LGPL
 - QCP demuxer
+- DivX (XSUB) subtitle encoder
 
 
 
Index: libavcodec/Makefile
===================================================================
--- libavcodec/Makefile	(revision 18911)
+++ libavcodec/Makefile	(working copy)
@@ -269,6 +269,7 @@
 OBJS-$(CONFIG_XAN_WC4_DECODER)         += xan.o
 OBJS-$(CONFIG_XL_DECODER)              += xl.o
 OBJS-$(CONFIG_XSUB_DECODER)            += xsubdec.o
+OBJS-$(CONFIG_XSUB_ENCODER)            += xsubenc.o
 OBJS-$(CONFIG_ZLIB_DECODER)            += lcldec.o
 OBJS-$(CONFIG_ZLIB_ENCODER)            += lclenc.o
 OBJS-$(CONFIG_ZMBV_DECODER)            += zmbv.o
Index: libavcodec/xsubenc.c
===================================================================
--- libavcodec/xsubenc.c	(revision 0)
+++ libavcodec/xsubenc.c	(revision 0)
@@ -0,0 +1,224 @@
+/*
+ * DivX (XSUB) subtitle encoder
+ * Copyright (c) 2005 DivX, Inc.
+ * Copyright (c) 2009 Bjorn Axelsson
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg 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
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "avcodec.h"
+#include "bytestream.h"
+#include "bitstream.h"
+
+/**
+ * Number of pixels to pad left and right.
+ *
+ * The official encoder pads the subtitles with two pixels on either side,
+ * but until we find out why we won't do it (we will pad to have width
+ * divisible by 2 though).
+ */
+#define PADDING 0
+#define PADDING_COLOR 0
+
+/**
+ * Encode a single color run. At most 16 bits will be used.
+ * \param len length of the run, values > 255 mean "until end of line", may not be < 0.
+ * \param color color to encode, only the lowest two bits are used and all others must be 0.
+ */
+static void put_xsub_rle(PutBitContext *pb, int len, int color)
+{
+    if (len <= 255)
+        put_bits(pb, 2 + ((ff_log2_tab[len] >> 1) << 2), len);
+    else
+        put_bits(pb, 14, 0);
+    put_bits(pb, 2, color);
+}
+
+/**
+ * Encode a 4-colour bitmap with XSUB rle.
+ *
+ * The encoded bitmap may be wider than the source bitmap due to padding.
+ */
+static int xsub_encode_rle(PutBitContext *pb, const uint8_t *bitmap,
+                           int linesize, int w, int h)
+{
+    int x0, x1, y, len, color = PADDING_COLOR;
+
+    for (y = 0; y < h; y++) {
+        x0 = 0;
+        while (x0 < w) {
+            // Make sure we have enough room for at least one run and padding
+            if (pb->size_in_bits - put_bits_count(pb) < 7*8)
+                return -1;
+
+            x1 = x0;
+            color = bitmap[x1++] & 3;
+            while (x1 < w && (bitmap[x1] & 3) == color)
+                x1++;
+            len = x1 - x0;
+            if (PADDING && x0 == 0) {
+                if (color == PADDING_COLOR) {
+                    len += PADDING;
+                    x0  -= PADDING;
+                } else
+                    put_xsub_rle(pb, PADDING, PADDING_COLOR);
+            }
+
+            // Run can't be longer than 255, unless it is the rest of a row
+            if (x1 == w && color == PADDING_COLOR) {
+                len += PADDING + (w&1);
+            } else
+                len = FFMIN(len, 255);
+            put_xsub_rle(pb, len, color);
+
+            x0 += len;
+        }
+        if (color != PADDING_COLOR && (PADDING + (w&1)))
+            put_xsub_rle(pb, PADDING + (w&1), PADDING_COLOR);
+
+        align_put_bits(pb);
+
+        bitmap += linesize;
+    }
+
+    return 0;
+}
+
+static int make_tc(uint64_t ms, int *tc)
+{
+    static const int tc_divs[3] = { 1000, 60, 60 };
+    int i;
+    for (i=0; i<3; i++) {
+        tc[i] = ms % tc_divs[i];
+        ms /= tc_divs[i];
+    }
+    tc[3] = ms;
+    return ms > 99;
+}
+
+static int xsub_encode(AVCodecContext *avctx, unsigned char *buf,
+                       int bufsize, void *data)
+{
+    AVSubtitle *h = data;
+    uint64_t startTime = h->pts / 1000; // FIXME: need better solution...
+    uint64_t endTime = startTime + h->end_display_time - h->start_display_time;
+    int start_tc[4], end_tc[4];
+    uint8_t *hdr = buf + 27; // Point behind the timestamp
+    uint8_t *rlelenptr;
+    uint16_t width, height;
+    int i;
+    PutBitContext pb;
+
+    if (bufsize < 27 + 7*2 + 4*3) {
+        av_log(avctx, AV_LOG_ERROR, "Buffer too small for XSUB header.\n");
+        return -1;
+    }
+
+    // TODO: support multiple rects
+    if (h->num_rects > 1)
+        av_log(avctx, AV_LOG_WARNING, "Only single rects supported (%d in subtitle.)\n", h->num_rects);
+
+    // TODO: render text-based subtitles into bitmaps
+    if (!h->rects[0]->pict.data[0] || !h->rects[0]->pict.data[1]) {
+        av_log(avctx, AV_LOG_WARNING, "No subtitle bitmap available.\n");
+        return -1;
+    }
+
+    // TODO: color reduction, similar to dvdsub encoder
+    if (h->rects[0]->nb_colors > 4)
+        av_log(avctx, AV_LOG_WARNING, "No more than 4 subtitle colors supported (%d found.)\n", h->rects[0]->nb_colors);
+
+    // TODO: Palette swapping if color zero is not transparent
+    if (((uint32_t *)h->rects[0]->pict.data[1])[0] & 0xff)
+        av_log(avctx, AV_LOG_WARNING, "Color index 0 is not transparent. Transparency will be messed up.\n");
+
+    if (make_tc(startTime, start_tc) || make_tc(endTime, end_tc)) {
+        av_log(avctx, AV_LOG_WARNING, "Time code >= 100 hours.\n");
+        return -1;
+    }
+
+    snprintf(buf, 28,
+        "[%02d:%02d:%02d.%03d-%02d:%02d:%02d.%03d]",
+        start_tc[3], start_tc[2], start_tc[1], start_tc[0],
+        end_tc[3],   end_tc[3],   end_tc[1],   end_tc[0]);
+
+    // Width and height must probably be multiples of 2.
+    // 2 pixels required on either side of subtitle.
+    // Possibly due to limitations of hardware renderers.
+    // TODO: check if the bitmap is already padded
+    width  = FFALIGN(h->rects[0]->w, 2) + PADDING * 2;
+    height = FFALIGN(h->rects[0]->h, 2);
+
+    bytestream_put_le16(&hdr, width);
+    bytestream_put_le16(&hdr, height);
+    bytestream_put_le16(&hdr, h->rects[0]->x);
+    bytestream_put_le16(&hdr, h->rects[0]->y);
+    bytestream_put_le16(&hdr, h->rects[0]->x + width);
+    bytestream_put_le16(&hdr, h->rects[0]->y + height);
+
+    rlelenptr = hdr; // Will store length of first field here later.
+    hdr+=2;
+
+    // Palette
+    for (i=0; i<4; i++)
+        bytestream_put_be24(&hdr, ((uint32_t *)h->rects[0]->pict.data[1])[i]);
+
+    // Bitmap
+    // RLE buffer. Reserve 2 bytes for possible padding after the last row.
+    init_put_bits(&pb, hdr, bufsize - (hdr - buf) - 2);
+    if (xsub_encode_rle(&pb,
+                h->rects[0]->pict.data[0],
+                h->rects[0]->pict.linesize[0]*2,
+                h->rects[0]->w, (h->rects[0]->h + 1) >> 1))
+        return -1;
+    bytestream_put_le16(&rlelenptr, put_bits_count(&pb) >> 3); // Length of first field
+
+    if (xsub_encode_rle(&pb,
+            h->rects[0]->pict.data[0] + h->rects[0]->pict.linesize[0],
+            h->rects[0]->pict.linesize[0]*2,
+            h->rects[0]->w, h->rects[0]->h >> 1))
+        return -1;
+
+    // Enforce total height to be be multiple of 2
+    if (h->rects[0]->h & 1) {
+        put_xsub_rle(&pb, h->rects[0]->w, PADDING_COLOR);
+        align_put_bits(&pb);
+    }
+
+    flush_put_bits(&pb);
+
+    return hdr - buf + put_bits_count(&pb)/8;
+}
+
+static av_cold int xsub_encoder_init(AVCodecContext *avctx)
+{
+    if (!avctx->codec_tag)
+        avctx->codec_tag = MKTAG('D','X','S','B');
+
+    return 0;
+}
+
+AVCodec xsub_encoder = {
+    "xsub",
+    CODEC_TYPE_SUBTITLE,
+    CODEC_ID_XSUB,
+    0,
+    xsub_encoder_init,
+    xsub_encode,
+    NULL,
+    .long_name = NULL_IF_CONFIG_SMALL("DivX subtitles (XSUB)"),
+};
Index: libavcodec/allcodecs.c
===================================================================
--- libavcodec/allcodecs.c	(revision 18911)
+++ libavcodec/allcodecs.c	(working copy)
@@ -298,7 +298,7 @@
     /* subtitles */
     REGISTER_ENCDEC  (DVBSUB, dvbsub);
     REGISTER_ENCDEC  (DVDSUB, dvdsub);
-    REGISTER_DECODER (XSUB, xsub);
+    REGISTER_ENCDEC  (XSUB, xsub);
 
     /* external libraries */
     REGISTER_ENCDEC  (LIBAMR_NB, libamr_nb);
Index: libavcodec/avcodec.h
===================================================================
--- libavcodec/avcodec.h	(revision 18911)
+++ libavcodec/avcodec.h	(working copy)
@@ -30,7 +30,7 @@
 #include "libavutil/avutil.h"
 
 #define LIBAVCODEC_VERSION_MAJOR 52
-#define LIBAVCODEC_VERSION_MINOR 29
+#define LIBAVCODEC_VERSION_MINOR 30
 #define LIBAVCODEC_VERSION_MICRO  0
 
 #define LIBAVCODEC_VERSION_INT  AV_VERSION_INT(LIBAVCODEC_VERSION_MAJOR, \
@@ -2721,6 +2721,7 @@
     uint32_t end_display_time; /* relative to packet pts, in ms */
     unsigned num_rects;
     AVSubtitleRect **rects;
+    int64_t pts;    ///< Same as packet pts, in AV_TIME_BASE
 } AVSubtitle;
 
 /* packet functions */
Index: doc/general.texi
===================================================================
--- doc/general.texi	(revision 18911)
+++ doc/general.texi	(working copy)
@@ -628,7 +628,7 @@
 @item SSA/ASS      @tab X @tab X
 @item DVB          @tab X @tab X @tab X @tab X
 @item DVD          @tab X @tab X @tab X @tab X
- at item XSUB         @tab   @tab   @tab   @tab X
+ at item XSUB         @tab   @tab   @tab X @tab X
 @end multitable
 
 @code{X} means that the feature is supported.
Index: libavformat/avienc.c
===================================================================
--- libavformat/avienc.c	(revision 18911)
+++ libavformat/avienc.c	(working copy)
@@ -81,6 +81,9 @@
     if (type == CODEC_TYPE_VIDEO) {
         tag[2] = 'd';
         tag[3] = 'c';
+    } else if (type == CODEC_TYPE_SUBTITLE) {
+        tag[2] = 's';
+        tag[3] = 'b';
     } else {
         tag[2] = 'w';
         tag[3] = 'b';
@@ -212,8 +215,10 @@
         case CODEC_TYPE_AUDIO: put_tag(pb, "auds"); break;
 //        case CODEC_TYPE_TEXT : put_tag(pb, "txts"); break;
         case CODEC_TYPE_DATA : put_tag(pb, "dats"); break;
+        case CODEC_TYPE_SUBTITLE: put_tag(pb, "vids"); break;
         }
-        if(stream->codec_type == CODEC_TYPE_VIDEO)
+        if(stream->codec_type == CODEC_TYPE_VIDEO
+                || stream->codec_type == CODEC_TYPE_SUBTITLE)
             put_le32(pb, stream->codec_tag);
         else
             put_le32(pb, 1);
@@ -253,6 +258,7 @@
         strf = start_tag(pb, "strf");
         switch(stream->codec_type) {
         case CODEC_TYPE_VIDEO:
+        case CODEC_TYPE_SUBTITLE:
             put_bmp_header(pb, stream, codec_bmp_tags, 0);
             break;
         case CODEC_TYPE_AUDIO:



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