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| 1 | +/* |
| 2 | + * Copyright (c) 2020 John Stebbins <jstebbins.hb@gmail.com> |
| 3 | + * |
| 4 | + * This file is part of FFmpeg. |
| 5 | + * |
| 6 | + * FFmpeg is free software; you can redistribute it and/or |
| 7 | + * modify it under the terms of the GNU Lesser General Public |
| 8 | + * License as published by the Free Software Foundation; either |
| 9 | + * version 2.1 of the License, or (at your option) any later version. |
| 10 | + * |
| 11 | + * FFmpeg is distributed in the hope that it will be useful, |
| 12 | + * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 13 | + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 14 | + * Lesser General Public License for more details. |
| 15 | + * |
| 16 | + * You should have received a copy of the GNU Lesser General Public |
| 17 | + * License along with FFmpeg; if not, write to the Free Software |
| 18 | + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 19 | + */ |
| 20 | + |
| 21 | +/** |
| 22 | + * @file |
| 23 | + * This bitstream filter merges PGS subtitle packets containing incomplete |
| 24 | + * set of segments into a single packet |
| 25 | + * |
| 26 | + * Packets already containing a complete set of segments will be passed through |
| 27 | + * unchanged. |
| 28 | + */ |
| 29 | + |
| 30 | +#include "libavutil/attributes.h" |
| 31 | +#include "libavutil/intreadwrite.h" |
| 32 | +#include "libavutil/log.h" |
| 33 | +#include "bsf.h" |
| 34 | +#include "bsf_internal.h" |
| 35 | + |
| 36 | +enum PGSSegmentType { |
| 37 | + PALETTE_SEGMENT = 0x14, |
| 38 | + OBJECT_SEGMENT = 0x15, |
| 39 | + PRESENTATION_SEGMENT = 0x16, |
| 40 | + WINDOW_SEGMENT = 0x17, |
| 41 | + END_DISPLAY_SET_SEGMENT = 0x80, |
| 42 | +}; |
| 43 | + |
| 44 | +typedef struct PGSMergeContext { |
| 45 | + AVPacket *buffer_pkt, *in; |
| 46 | + int presentation_found; |
| 47 | + int pkt_flags; |
| 48 | +} PGSMergeContext; |
| 49 | + |
| 50 | +static av_cold void frame_merge_flush(AVBSFContext *bsf) |
| 51 | +{ |
| 52 | + PGSMergeContext *ctx = bsf->priv_data; |
| 53 | + |
| 54 | + ctx->presentation_found = ctx->pkt_flags = 0; |
| 55 | + av_packet_unref(ctx->in); |
| 56 | + av_packet_unref(ctx->buffer_pkt); |
| 57 | +} |
| 58 | + |
| 59 | +static int frame_merge_output(PGSMergeContext *ctx, AVPacket *dst, AVPacket *src) |
| 60 | +{ |
| 61 | + if (!ctx->presentation_found) |
| 62 | + ctx->pkt_flags |= AV_PKT_FLAG_CORRUPT; |
| 63 | + ctx->presentation_found = 0; |
| 64 | + src->flags |= ctx->pkt_flags; |
| 65 | + ctx->pkt_flags = 0; |
| 66 | + av_packet_move_ref(dst, src); |
| 67 | + return 0; |
| 68 | +} |
| 69 | + |
| 70 | +static int frame_merge_filter(AVBSFContext *bsf, AVPacket *out) |
| 71 | +{ |
| 72 | + PGSMergeContext *ctx = bsf->priv_data; |
| 73 | + AVPacket *in = ctx->in, *pkt = ctx->buffer_pkt; |
| 74 | + int ret, size, pos, display = 0, presentation = 0; |
| 75 | + unsigned int i; |
| 76 | + |
| 77 | + if (!in->data) { |
| 78 | + ret = ff_bsf_get_packet_ref(bsf, in); |
| 79 | + if (ret == AVERROR_EOF && pkt->data) { |
| 80 | + // Output remaining data |
| 81 | + ctx->pkt_flags |= AV_PKT_FLAG_CORRUPT; |
| 82 | + return frame_merge_output(ctx, out, pkt); |
| 83 | + } |
| 84 | + if (ret < 0) |
| 85 | + return ret; |
| 86 | + } |
| 87 | + if (!in->size) { |
| 88 | + av_packet_unref(in); |
| 89 | + return AVERROR(EAGAIN); |
| 90 | + } |
| 91 | + in->flags &= ~AV_PKT_FLAG_KEY; // Will be detected in the stream |
| 92 | + |
| 93 | + // Validate packet data and find display_end segment |
| 94 | + size = in->size; |
| 95 | + i = 0; |
| 96 | + while (i + 3 <= in->size) { |
| 97 | + uint8_t segment_type = in->data[i]; |
| 98 | + int segment_len = AV_RB16(in->data + i + 1) + 3; |
| 99 | + |
| 100 | + if (i + segment_len > in->size) |
| 101 | + break; // Invalid, segments can't span packets |
| 102 | + if (segment_type == PRESENTATION_SEGMENT && ctx->presentation_found) |
| 103 | + break; // Invalid, there can be only one |
| 104 | + if (segment_type == PRESENTATION_SEGMENT) { |
| 105 | + uint8_t state; |
| 106 | + if (segment_len < 11) |
| 107 | + break; // Invalid presentation segment length |
| 108 | + ctx->presentation_found = presentation = 1; |
| 109 | + state = in->data[i + 10] & 0xc0; |
| 110 | + if (state) |
| 111 | + ctx->pkt_flags |= AV_PKT_FLAG_KEY; |
| 112 | + else |
| 113 | + ctx->pkt_flags &= ~AV_PKT_FLAG_KEY; |
| 114 | + } |
| 115 | + i += segment_len; |
| 116 | + if (segment_type == END_DISPLAY_SET_SEGMENT) { |
| 117 | + size = i; |
| 118 | + display = 1; |
| 119 | + break; |
| 120 | + } |
| 121 | + } |
| 122 | + if (display && pkt->size == 0 && size == in->size) // passthrough |
| 123 | + return frame_merge_output(ctx, out, in); |
| 124 | + if (!display && i != in->size) { |
| 125 | + av_log(bsf, AV_LOG_WARNING, "Failed to parse PGS segments.\n"); |
| 126 | + // force output what we have |
| 127 | + size = in->size; |
| 128 | + display = 1; |
| 129 | + ctx->pkt_flags |= AV_PKT_FLAG_CORRUPT; |
| 130 | + } |
| 131 | + |
| 132 | + if (presentation) { |
| 133 | + ret = av_packet_copy_props(pkt, in); |
| 134 | + if (ret < 0) |
| 135 | + goto fail; |
| 136 | + } |
| 137 | + pos = pkt->size; |
| 138 | + ret = av_grow_packet(pkt, size); |
| 139 | + if (ret < 0) |
| 140 | + goto fail; |
| 141 | + memcpy(pkt->data + pos, in->data, size); |
| 142 | + |
| 143 | + if (size == in->size) |
| 144 | + av_packet_unref(in); |
| 145 | + else { |
| 146 | + in->data += size; |
| 147 | + in->size -= size; |
| 148 | + } |
| 149 | + |
| 150 | + if (display) |
| 151 | + return frame_merge_output(ctx, out, pkt); |
| 152 | + return AVERROR(EAGAIN); |
| 153 | + |
| 154 | +fail: |
| 155 | + frame_merge_flush(bsf); |
| 156 | + return ret; |
| 157 | +} |
| 158 | + |
| 159 | +static av_cold int frame_merge_init(AVBSFContext *bsf) |
| 160 | +{ |
| 161 | + PGSMergeContext *ctx = bsf->priv_data; |
| 162 | + |
| 163 | + ctx->in = av_packet_alloc(); |
| 164 | + ctx->buffer_pkt = av_packet_alloc(); |
| 165 | + if (!ctx->in || !ctx->buffer_pkt) |
| 166 | + return AVERROR(ENOMEM); |
| 167 | + |
| 168 | + return 0; |
| 169 | +} |
| 170 | + |
| 171 | +static av_cold void frame_merge_close(AVBSFContext *bsf) |
| 172 | +{ |
| 173 | + PGSMergeContext *ctx = bsf->priv_data; |
| 174 | + |
| 175 | + av_packet_free(&ctx->in); |
| 176 | + av_packet_free(&ctx->buffer_pkt); |
| 177 | +} |
| 178 | + |
| 179 | +static const enum AVCodecID frame_merge_codec_ids[] = { |
| 180 | + AV_CODEC_ID_HDMV_PGS_SUBTITLE, AV_CODEC_ID_NONE, |
| 181 | +}; |
| 182 | + |
| 183 | +const FFBitStreamFilter ff_pgs_frame_merge_bsf = { |
| 184 | + .p.name = "pgs_frame_merge", |
| 185 | + .p.codec_ids = frame_merge_codec_ids, |
| 186 | + .priv_data_size = sizeof(PGSMergeContext), |
| 187 | + .init = frame_merge_init, |
| 188 | + .flush = frame_merge_flush, |
| 189 | + .close = frame_merge_close, |
| 190 | + .filter = frame_merge_filter, |
| 191 | +}; |