[FFmpeg-devel] [PATCH 3/4] lavc/pgs_frame_split_bsf: add bsf to split PGS segments
Andreas Rheinhardt
andreas.rheinhardt at gmail.com
Sun May 3 00:05:28 EEST 2020
John Stebbins:
> Requried to remux mkv to m2ts
> ---
> Changelog | 1 +
> doc/bitstream_filters.texi | 8 ++
> libavcodec/Makefile | 1 +
> libavcodec/bitstream_filters.c | 1 +
> libavcodec/pgs_frame_split_bsf.c | 176 +++++++++++++++++++++++++++++++
> 5 files changed, 187 insertions(+)
> create mode 100644 libavcodec/pgs_frame_split_bsf.c
>
> diff --git a/Changelog b/Changelog
> index fec4867488..372bb4694c 100644
> --- a/Changelog
> +++ b/Changelog
> @@ -60,6 +60,7 @@ version <next>:
> - Expanded styling support for 3GPP Timed Text Subtitles (movtext)
> - WebP parser
> - PGS subtitle frame merge bitstream filter
> +- PGS subtitle frame split bitstream filter
>
>
> version 4.2:
> diff --git a/doc/bitstream_filters.texi b/doc/bitstream_filters.texi
> index 21ed09986c..643c419076 100644
> --- a/doc/bitstream_filters.texi
> +++ b/doc/bitstream_filters.texi
> @@ -556,6 +556,14 @@ segment into a single packet.
> This is required by some containers that support PGS subtitles
> (muxer @code{matroska}).
>
> + at section pgs_frame_split
> +
> +Split a packet containing a sequence of PGS Subtitle segments into separate
> +packets each containing a single segment.
> +
> +This is required by some streaming formats, typically the MPEG-2
> +transport stream format (muxer @code{mpegts}).
Is there a reason you don't add this bsf automatically for ts?
> +
> @section prores_metadata
>
> Modify color property metadata embedded in prores stream.
> diff --git a/libavcodec/Makefile b/libavcodec/Makefile
> index b630de21bc..0e5f2db192 100644
> --- a/libavcodec/Makefile
> +++ b/libavcodec/Makefile
> @@ -1116,6 +1116,7 @@ OBJS-$(CONFIG_MPEG2_METADATA_BSF) += mpeg2_metadata_bsf.o
> OBJS-$(CONFIG_NOISE_BSF) += noise_bsf.o
> OBJS-$(CONFIG_NULL_BSF) += null_bsf.o
> OBJS-$(CONFIG_PGS_FRAME_MERGE_BSF) += pgs_frame_merge_bsf.o
> +OBJS-$(CONFIG_PGS_FRAME_SPLIT_BSF) += pgs_frame_split_bsf.o
> OBJS-$(CONFIG_PRORES_METADATA_BSF) += prores_metadata_bsf.o
> OBJS-$(CONFIG_REMOVE_EXTRADATA_BSF) += remove_extradata_bsf.o
> OBJS-$(CONFIG_TEXT2MOVSUB_BSF) += movsub_bsf.o
> diff --git a/libavcodec/bitstream_filters.c b/libavcodec/bitstream_filters.c
> index 92619225f0..02e72c9ca5 100644
> --- a/libavcodec/bitstream_filters.c
> +++ b/libavcodec/bitstream_filters.c
> @@ -50,6 +50,7 @@ extern const AVBitStreamFilter ff_mov2textsub_bsf;
> extern const AVBitStreamFilter ff_noise_bsf;
> extern const AVBitStreamFilter ff_null_bsf;
> extern const AVBitStreamFilter ff_pgs_frame_merge_bsf;
> +extern const AVBitStreamFilter ff_pgs_frame_split_bsf;
> extern const AVBitStreamFilter ff_prores_metadata_bsf;
> extern const AVBitStreamFilter ff_remove_extradata_bsf;
> extern const AVBitStreamFilter ff_text2movsub_bsf;
> diff --git a/libavcodec/pgs_frame_split_bsf.c b/libavcodec/pgs_frame_split_bsf.c
> new file mode 100644
> index 0000000000..c983f6acf5
> --- /dev/null
> +++ b/libavcodec/pgs_frame_split_bsf.c
> @@ -0,0 +1,176 @@
> +/*
> + * 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 splits PGS subtitle packets into packets containing
> + * just one segment.
> + *
> + * Packets already containing only one segment 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 PGSSplitContext {
> + AVPacket *in;
> +} PGSSplitContext;
> +
> +static int frame_split_filter(AVBSFContext *bsf, AVPacket *out)
> +{
> + PGSSplitContext *ctx = bsf->priv_data;
> + AVPacket *in = ctx->in;
> + int i, ret;
> + uint8_t segment_type;
> + uint16_t segment_len;
> + int split = !!in->data;
> +
> + 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
> + i = 0;
> + while (i < in->size) {
> + segment_type = in->data[i];
> + segment_len = AV_RB16(in->data + i + 1) + 3;
uint16_t is not enough for segment_len. Also you are possibly
overreading here.
> + i += segment_len;
Possible overflow.
> + }
> + if (i != in->size) {
> + av_log(bsf, AV_LOG_WARNING, "Failed to parse PGS segments.\n");
If you output invalid data, you need to set the AV_PKT_FLAG_CORRUPT flag.
> + av_packet_move_ref(out, in);
> + return 0;
> + }
> +
> + segment_type = in->data[0];
> + segment_len = AV_RB16(in->data + 1) + 3;
> + if (split || segment_len < in->size) { // Split
> + int64_t ts_delta, dts;
> +
> + ret = av_packet_ref(out, in);
> + if (ret < 0)
> + goto fail;
> + out->size = segment_len;
> + in->data += segment_len;
> + in->size -= segment_len;
> +
> + // Update PTS/DTS, Stagger timestamps by 3ms
Where does this number come from?
> + ts_delta = 270; // Assume 90khz tick if no time_base_in
> + if (bsf->time_base_in.num && bsf->time_base_in.den)
> + ts_delta = bsf->time_base_in.den / bsf->time_base_in.num / 333;
> + if (ts_delta == 0)
> + ts_delta = 1;
> +
> + // Compute DTS, it's the same for all packets that carry it
> + // Assuming input PTS/DTS come from original presentation_segment
> + if (in->dts <= in->pts - 2 * ts_delta &&
> + in->dts != AV_NOPTS_VALUE)
> + dts = in->dts;
> + else if (in->pts != AV_NOPTS_VALUE)
> + dts = in->pts - 2 * ts_delta;
> +
> + switch (segment_type) {
> + case DISPLAY_SEGMENT:
> + if (in->pts != AV_NOPTS_VALUE)
> + out->pts = in->pts - ts_delta;
> + out->dts = AV_NOPTS_VALUE;
> + break;
> + case PALETTE_SEGMENT:
> + if (in->pts != AV_NOPTS_VALUE)
> + out->pts = in->pts - 2 * ts_delta;
> + out->dts = AV_NOPTS_VALUE;
> + break;
> + case PRESENTATION_SEGMENT:
> + out->pts = in->pts;
> + out->dts = dts;
> + break;
> + case WINDOW_SEGMENT:
> + case OBJECT_SEGMENT:
> + default:
> + if (in->pts != AV_NOPTS_VALUE)
> + out->pts = in->pts - ts_delta;
> + out->dts = dts;
> + break;
> + }
> + } else
> + av_packet_move_ref(out, in);
> +
> + return 0;
> +
> +fail:
> + av_packet_unref(in);
> +
> + return ret;
> +}
> +
> +static int frame_split_init(AVBSFContext *bsf)
> +{
> + PGSSplitContext *ctx = bsf->priv_data;
> +
> + ctx->in = av_packet_alloc();
> + if (!ctx->in)
> + return AVERROR(ENOMEM);
> +
> + return 0;
> +}
> +
> +static void frame_split_flush(AVBSFContext *bsf)
> +{
> + PGSSplitContext *ctx = bsf->priv_data;
> +
> + av_packet_unref(ctx->in);
> +}
> +
> +static void frame_split_close(AVBSFContext *bsf)
> +{
> + PGSSplitContext *ctx = bsf->priv_data;
> +
> + av_packet_free(&ctx->in);
> +}
> +
> +static const enum AVCodecID frame_split_codec_ids[] = {
> + AV_CODEC_ID_HDMV_PGS_SUBTITLE, AV_CODEC_ID_NONE,
> +};
> +
> +const AVBitStreamFilter ff_pgs_frame_split_bsf = {
> + .name = "pgs_frame_split",
> + .priv_data_size = sizeof(PGSSplitContext),
> + .init = frame_split_init,
> + .flush = frame_split_flush,
> + .close = frame_split_close,
> + .filter = frame_split_filter,
> + .codec_ids = frame_split_codec_ids,
> +};
>
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