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c602deb138
write_packet() has code to shift the packets timestamps to make them nonnegative or even make them start at ts zero; this code inspects every packet that is written and if a packet with negative timestamp (whether this is dts or pts depends upon another flag; basically: Matroska uses pts, everyone else dts) is encountered, this is offset to make the timestamp zero. All further packets will be offset accordingly (with the offset converted according to the streams' timebases). This is based around an assumption, namely that the timestamps are indeed non-decreasing, so that the first packet with negative timestamps is the first packet with timestamps. This assumption is often fulfilled given that the default interleavement function by default interleaves per dts; yet there are scenarios in which it may not be fulfilled: a) av_write_frame() instead of av_interleaved_write_frame() is used. b) The audio_preload option is used. c) When the timestamps that are made nonnegative/zero are pts (i.e. with Matroska), because the packet with the smallest dts is not necessarily the packet with the smallest pts. d) Possibly with custom interleavement functions. In these cases the relative sync of the first few packet(s) is offset relative to the later packets. This contradicts the documentation ("When shifting is enabled, all output timestamps are shifted by the same amount"). Therefore this commit changes this: As soon as the first packet with valid timestamps is output, it is checked and recorded whether the timestamps need to be shifted. Further packets are no longer checked for needing to be offset; instead they are simply offset. In the cases above this leads to packets with negative timestamps (and the appropriate warnings) instead of desync. This will mostly be fixed in the next commit. This commit also factors handling the avoid_negative_ts stuff out of write_packet() in order to be able to return immediately. Tickets #4536 and #5784 as well as the matroska-avoid-negative-ts-test are examples of c); as has been said, some timestamps are now negative, yet the ref file update does not show it because ffmpeg.c sanitizes the timestamps (-copyts disables it; ffprobe and mkvinfo also show the original timestamps). Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
191 lines
5.1 KiB
C
191 lines
5.1 KiB
C
/*
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* Copyright (c) 2000, 2001, 2002 Fabrice Bellard
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avformat.h"
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#include "avio_internal.h"
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#include "internal.h"
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#include "libavutil/avassert.h"
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#include "libavutil/internal.h"
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#include "libavutil/opt.h"
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/**
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* @file
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* Options definition for AVFormatContext.
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*/
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FF_DISABLE_DEPRECATION_WARNINGS
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#include "options_table.h"
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FF_ENABLE_DEPRECATION_WARNINGS
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static const char* format_to_name(void* ptr)
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{
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AVFormatContext* fc = (AVFormatContext*) ptr;
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if(fc->iformat) return fc->iformat->name;
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else if(fc->oformat) return fc->oformat->name;
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else return "NULL";
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}
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static void *format_child_next(void *obj, void *prev)
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{
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AVFormatContext *s = obj;
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if (!prev && s->priv_data &&
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((s->iformat && s->iformat->priv_class) ||
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s->oformat && s->oformat->priv_class))
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return s->priv_data;
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if (s->pb && s->pb->av_class && prev != s->pb)
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return s->pb;
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return NULL;
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}
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enum {
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CHILD_CLASS_ITER_AVIO = 0,
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CHILD_CLASS_ITER_MUX,
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CHILD_CLASS_ITER_DEMUX,
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CHILD_CLASS_ITER_DONE,
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};
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#define ITER_STATE_SHIFT 16
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static const AVClass *format_child_class_iterate(void **iter)
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{
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// we use the low 16 bits of iter as the value to be passed to
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// av_(de)muxer_iterate()
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void *val = (void*)(((uintptr_t)*iter) & ((1 << ITER_STATE_SHIFT) - 1));
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unsigned int state = ((uintptr_t)*iter) >> ITER_STATE_SHIFT;
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const AVClass *ret = NULL;
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if (state == CHILD_CLASS_ITER_AVIO) {
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ret = &ff_avio_class;
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state++;
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goto finish;
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}
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if (state == CHILD_CLASS_ITER_MUX) {
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const AVOutputFormat *ofmt;
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while ((ofmt = av_muxer_iterate(&val))) {
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ret = ofmt->priv_class;
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if (ret)
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goto finish;
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}
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val = NULL;
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state++;
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}
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if (state == CHILD_CLASS_ITER_DEMUX) {
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const AVInputFormat *ifmt;
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while ((ifmt = av_demuxer_iterate(&val))) {
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ret = ifmt->priv_class;
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if (ret)
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goto finish;
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}
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val = NULL;
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state++;
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}
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finish:
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// make sure none av_(de)muxer_iterate does not set the high bits of val
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av_assert0(!((uintptr_t)val >> ITER_STATE_SHIFT));
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*iter = (void*)((uintptr_t)val | (state << ITER_STATE_SHIFT));
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return ret;
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}
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static AVClassCategory get_category(void *ptr)
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{
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AVFormatContext* s = ptr;
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if(s->iformat) return AV_CLASS_CATEGORY_DEMUXER;
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else return AV_CLASS_CATEGORY_MUXER;
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}
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static const AVClass av_format_context_class = {
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.class_name = "AVFormatContext",
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.item_name = format_to_name,
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.option = avformat_options,
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.version = LIBAVUTIL_VERSION_INT,
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.child_next = format_child_next,
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.child_class_iterate = format_child_class_iterate,
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.category = AV_CLASS_CATEGORY_MUXER,
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.get_category = get_category,
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};
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static int io_open_default(AVFormatContext *s, AVIOContext **pb,
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const char *url, int flags, AVDictionary **options)
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{
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int loglevel;
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if (!strcmp(url, s->url) ||
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s->iformat && !strcmp(s->iformat->name, "image2") ||
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s->oformat && !strcmp(s->oformat->name, "image2")
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) {
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loglevel = AV_LOG_DEBUG;
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} else
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loglevel = AV_LOG_INFO;
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av_log(s, loglevel, "Opening \'%s\' for %s\n", url, flags & AVIO_FLAG_WRITE ? "writing" : "reading");
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return ffio_open_whitelist(pb, url, flags, &s->interrupt_callback, options, s->protocol_whitelist, s->protocol_blacklist);
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}
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static int io_close2_default(AVFormatContext *s, AVIOContext *pb)
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{
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return avio_close(pb);
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}
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AVFormatContext *avformat_alloc_context(void)
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{
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FFFormatContext *const si = av_mallocz(sizeof(*si));
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AVFormatContext *s;
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if (!si)
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return NULL;
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s = &si->pub;
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s->av_class = &av_format_context_class;
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s->io_open = io_open_default;
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s->io_close = ff_format_io_close_default;
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s->io_close2= io_close2_default;
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av_opt_set_defaults(s);
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si->pkt = av_packet_alloc();
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si->parse_pkt = av_packet_alloc();
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if (!si->pkt || !si->parse_pkt) {
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avformat_free_context(s);
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return NULL;
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}
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si->shortest_end = AV_NOPTS_VALUE;
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return s;
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}
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enum AVDurationEstimationMethod av_fmt_ctx_get_duration_estimation_method(const AVFormatContext* ctx)
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{
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return ctx->duration_estimation_method;
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}
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const AVClass *avformat_get_class(void)
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{
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return &av_format_context_class;
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}
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