[FFmpeg-devel] [PATCH 1/3] lavc/pgs_frame_merge_bsf: add bsf to merge PGS segments

[John Stebbins]

Required to remux m2ts to mkv
---
 libavcodec/Makefile              |   1 +
 libavcodec/bitstream_filters.c   |   1 +
 libavcodec/pgs_frame_merge_bsf.c | 152 +++++++++++++++++++++++++++++++
 3 files changed, 154 insertions(+)
 create mode 100644 libavcodec/pgs_frame_merge_bsf.c

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index c1c9a44f2b..13909faabf 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -1119,6 +1119,7 @@ OBJS-$(CONFIG_VP9_METADATA_BSF)           += vp9_metadata_bsf.o
 OBJS-$(CONFIG_VP9_RAW_REORDER_BSF)        += vp9_raw_reorder_bsf.o
 OBJS-$(CONFIG_VP9_SUPERFRAME_BSF)         += vp9_superframe_bsf.o
 OBJS-$(CONFIG_VP9_SUPERFRAME_SPLIT_BSF)   += vp9_superframe_split_bsf.o
+OBJS-$(CONFIG_PGS_FRAME_MERGE_BSF)        += pgs_frame_merge_bsf.o
 
 # thread libraries
 OBJS-$(HAVE_LIBC_MSVCRT)               += file_open.o
diff --git a/libavcodec/bitstream_filters.c b/libavcodec/bitstream_filters.c
index 6b5ffe4d70..138f6dd7ad 100644
--- a/libavcodec/bitstream_filters.c
+++ b/libavcodec/bitstream_filters.c
@@ -58,6 +58,7 @@ extern const AVBitStreamFilter ff_vp9_metadata_bsf;
 extern const AVBitStreamFilter ff_vp9_raw_reorder_bsf;
 extern const AVBitStreamFilter ff_vp9_superframe_bsf;
 extern const AVBitStreamFilter ff_vp9_superframe_split_bsf;
+extern const AVBitStreamFilter ff_pgs_frame_merge_bsf;
 
 #include "libavcodec/bsf_list.c"
 
diff --git a/libavcodec/pgs_frame_merge_bsf.c b/libavcodec/pgs_frame_merge_bsf.c
new file mode 100644
index 0000000000..4b8061d4e1
--- /dev/null
+++ b/libavcodec/pgs_frame_merge_bsf.c
@@ -0,0 +1,152 @@
+/*
+ * Copyright (c) 2020 John Stebbins <jstebbins.hb at gmail.com>
+ *
+ * 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
+ */
+
+/**
+ * @file
+ * This bitstream filter merges PGS subtitle packets containing incomplete
+ * set of segments into a single packet
+ *
+ * Packets already containing a complete set of segments will be passed through
+ * unchanged.
+ */
+
+#include "avcodec.h"
+#include "bsf.h"
+#include "libavutil/intreadwrite.h"
+
+enum PGSSegmentType {
+    PALETTE_SEGMENT      = 0x14,
+    OBJECT_SEGMENT       = 0x15,
+    PRESENTATION_SEGMENT = 0x16,
+    WINDOW_SEGMENT       = 0x17,
+    DISPLAY_SEGMENT      = 0x80,
+};
+
+typedef struct PGSMergeContext {
+    AVPacket *buffer_pkt, *in;
+} PGSMergeContext;
+
+static void frame_merge_flush(AVBSFContext *bsf)
+{
+    PGSMergeContext *ctx = bsf->priv_data;
+
+    av_packet_unref(ctx->in);
+    av_packet_unref(ctx->buffer_pkt);
+}
+
+static int frame_merge_filter(AVBSFContext *bsf, AVPacket *out)
+{
+    PGSMergeContext *ctx = bsf->priv_data;
+    AVPacket *in = ctx->in, *pkt = ctx->buffer_pkt;
+    int ret, i, size, pos, display = 0;
+    uint8_t segment_type;
+    uint16_t segment_len;
+
+    if (!in->data) {
+        ret = ff_bsf_get_packet_ref(bsf, in);
+        if (ret < 0)
+            return ret;
+    }
+    if (!in->size) {
+        av_packet_unref(in);
+        return AVERROR(EAGAIN);
+    }
+
+    // Validate packet data and find display_end segment
+    size = in->size;
+    i = 0;
+    while (i < in->size) {
+        segment_type = in->data[i];
+        segment_len  = AV_RB16(in->data + i + 1) + 3;
+        if (segment_type == DISPLAY_SEGMENT) {
+            size = display = i + segment_len;
+            break;
+        }
+        if (segment_type == PRESENTATION_SEGMENT) {
+            av_packet_copy_props(pkt, in);
+            pkt->pts = in->pts;
+            pkt->dts = in->dts;
+        }
+        i += segment_len;
+    }
+    if ((!display && i != in->size) || size > in->size) {
+        av_log(ctx, AV_LOG_WARNING, "Failed to parse PGS segments.\n");
+        // force output what we have
+        display = size = in->size;;
+    }
+
+    pos = pkt->size;
+    ret = av_grow_packet(pkt, size);
+    if (ret < 0)
+        goto fail;
+    memcpy(pkt->data + pos, in->data, size);
+
+    if (size == in->size)
+        av_packet_unref(in);
+    else {
+        in->data += size;
+        in->size -= size;
+    }
+
+    if (display) {
+        av_packet_move_ref(out, pkt);
+        av_packet_copy_props(pkt, out);
+        return 0;
+    }
+    return AVERROR(EAGAIN);
+
+fail:
+    frame_merge_flush(bsf);
+    return ret;
+}
+
+static int frame_merge_init(AVBSFContext *bsf)
+{
+    PGSMergeContext *ctx = bsf->priv_data;
+
+    ctx->in  = av_packet_alloc();
+    ctx->buffer_pkt = av_packet_alloc();
+    if (!ctx->in || !ctx->buffer_pkt)
+        return AVERROR(ENOMEM);
+
+    return 0;
+}
+
+static void frame_merge_close(AVBSFContext *bsf)
+{
+    PGSMergeContext *ctx = bsf->priv_data;
+
+    av_packet_free(&ctx->in);
+    av_packet_free(&ctx->buffer_pkt);
+}
+
+static const enum AVCodecID frame_merge_codec_ids[] = {
+    AV_CODEC_ID_HDMV_PGS_SUBTITLE, AV_CODEC_ID_NONE,
+};
+
+const AVBitStreamFilter ff_pgs_frame_merge_bsf = {
+    .name           = "pgs_frame_merge",
+    .priv_data_size = sizeof(PGSMergeContext),
+    .init           = frame_merge_init,
+    .flush          = frame_merge_flush,
+    .close          = frame_merge_close,
+    .filter         = frame_merge_filter,
+    .codec_ids      = frame_merge_codec_ids,
+};
-- 
2.25.2