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/*
* Copyright (c) 2020 John Stebbins <jstebbins.hb@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 "libavutil/attributes.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"
#include "bsf.h"
#include "bsf_internal.h"
enum PGSSegmentType {
PALETTE_SEGMENT = 0x14,
OBJECT_SEGMENT = 0x15,
PRESENTATION_SEGMENT = 0x16,
WINDOW_SEGMENT = 0x17,
END_DISPLAY_SET_SEGMENT = 0x80,
};
typedef struct PGSMergeContext {
AVPacket *buffer_pkt, *in;
int presentation_found;
int pkt_flags;
} PGSMergeContext;
static av_cold void frame_merge_flush(AVBSFContext *bsf)
{
PGSMergeContext *ctx = bsf->priv_data;
ctx->presentation_found = ctx->pkt_flags = 0;
av_packet_unref(ctx->in);
av_packet_unref(ctx->buffer_pkt);
}
static int frame_merge_output(PGSMergeContext *ctx, AVPacket *dst, AVPacket *src)
{
if (!ctx->presentation_found)
ctx->pkt_flags |= AV_PKT_FLAG_CORRUPT;
ctx->presentation_found = 0;
src->flags |= ctx->pkt_flags;
ctx->pkt_flags = 0;
av_packet_move_ref(dst, src);
return 0;
}
static int frame_merge_filter(AVBSFContext *bsf, AVPacket *out)
{
PGSMergeContext *ctx = bsf->priv_data;
AVPacket *in = ctx->in, *pkt = ctx->buffer_pkt;
int ret, size, pos, display = 0, presentation = 0;
unsigned int i;
if (!in->data) {
ret = ff_bsf_get_packet_ref(bsf, in);
if (ret == AVERROR_EOF && pkt->data) {
// Output remaining data
ctx->pkt_flags |= AV_PKT_FLAG_CORRUPT;
return frame_merge_output(ctx, out, pkt);
}
if (ret < 0)
return ret;
}
if (!in->size) {
av_packet_unref(in);
return AVERROR(EAGAIN);
}
in->flags &= ~AV_PKT_FLAG_KEY; // Will be detected in the stream
// Validate packet data and find display_end segment
size = in->size;
i = 0;
while (i + 3 <= in->size) {
uint8_t segment_type = in->data[i];
int segment_len = AV_RB16(in->data + i + 1) + 3;
if (i + segment_len > in->size)
break; // Invalid, segments can't span packets
if (segment_type == PRESENTATION_SEGMENT && ctx->presentation_found)
break; // Invalid, there can be only one
if (segment_type == PRESENTATION_SEGMENT) {
uint8_t state;
if (segment_len < 11)
break; // Invalid presentation segment length
ctx->presentation_found = presentation = 1;
state = in->data[i + 10] & 0xc0;
if (state)
ctx->pkt_flags |= AV_PKT_FLAG_KEY;
else
ctx->pkt_flags &= ~AV_PKT_FLAG_KEY;
}
i += segment_len;
if (segment_type == END_DISPLAY_SET_SEGMENT) {
size = i;
display = 1;
break;
}
}
if (display && pkt->size == 0 && size == in->size) // passthrough
return frame_merge_output(ctx, out, in);
if (!display && i != in->size) {
av_log(bsf, AV_LOG_WARNING, "Failed to parse PGS segments.\n");
// force output what we have
size = in->size;
display = 1;
ctx->pkt_flags |= AV_PKT_FLAG_CORRUPT;
}
if (presentation) {
ret = av_packet_copy_props(pkt, in);
if (ret < 0)
goto fail;
}
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)
return frame_merge_output(ctx, out, pkt);
return AVERROR(EAGAIN);
fail:
frame_merge_flush(bsf);
return ret;
}
static av_cold 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 av_cold 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 FFBitStreamFilter ff_pgs_frame_merge_bsf = {
.p.name = "pgs_frame_merge",
.p.codec_ids = frame_merge_codec_ids,
.priv_data_size = sizeof(PGSMergeContext),
.init = frame_merge_init,
.flush = frame_merge_flush,
.close = frame_merge_close,
.filter = frame_merge_filter,
};
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