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diff --git a/common/recorder.c b/common/recorder.c
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+++ b/common/recorder.c
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+/*
+ * This file is part of mpv.
+ *
+ * mpv 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.
+ *
+ * mpv 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 mpv. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <math.h>
+
+#include <libavformat/avformat.h>
+
+#include "common/av_common.h"
+#include "common/common.h"
+#include "common/global.h"
+#include "common/msg.h"
+#include "demux/packet.h"
+#include "demux/stheader.h"
+
+#include "recorder.h"
+
+#define PTS_ADD(a, b) ((a) == MP_NOPTS_VALUE ? (a) : ((a) + (b)))
+
+// Maximum number of packets we buffer at most to attempt to resync streams.
+// Essentially, this should be higher than the highest supported keyframe
+// interval.
+#define QUEUE_MAX_PACKETS 256
+// Number of packets we should buffer at least to determine timestamps (due to
+// codec delay and frame reordering, and potentially lack of DTS).
+// Keyframe flags can trigger this earlier.
+#define QUEUE_MIN_PACKETS 16
+
+struct mp_recorder {
+ struct mpv_global *global;
+ struct mp_log *log;
+
+ struct mp_recorder_sink **streams;
+ int num_streams;
+
+ bool opened; // mux context is valid
+ bool muxing; // we're currently recording (instead of preparing)
+ bool muxing_from_start; // no discontinuity at start
+ bool dts_warning;
+
+ // The start timestamp of the currently recorded segment (the timestamp of
+ // the first packet of the incoming packet stream).
+ double base_ts;
+ // The output packet timestamp corresponding to base_ts. It's the timestamp
+ // of the first packet of the current segment written to the output.
+ double rebase_ts;
+
+ AVFormatContext *mux;
+};
+
+struct mp_recorder_sink {
+ struct mp_recorder *owner;
+ struct sh_stream *sh;
+ AVStream *av_stream;
+ double max_out_pts;
+ bool discont;
+ bool proper_eof;
+ struct demux_packet **packets;
+ int num_packets;
+};
+
+static int add_stream(struct mp_recorder *priv, struct sh_stream *sh)
+{
+ enum AVMediaType av_type = mp_to_av_stream_type(sh->type);
+ if (av_type == AVMEDIA_TYPE_UNKNOWN)
+ return -1;
+
+ struct mp_recorder_sink *rst = talloc(priv, struct mp_recorder_sink);
+ *rst = (struct mp_recorder_sink) {
+ .owner = priv,
+ .sh = sh,
+ .av_stream = avformat_new_stream(priv->mux, NULL),
+ .max_out_pts = MP_NOPTS_VALUE,
+ };
+
+ if (!rst->av_stream)
+ return -1;
+
+ AVCodecParameters *avp = mp_codec_params_to_av(sh->codec);
+ if (!avp)
+ return -1;
+
+#if LIBAVCODEC_VERSION_MICRO >= 100
+ // We don't know the delay, so make something up. If the format requires
+ // DTS, the result will probably be broken. FFmpeg provides nothing better
+ // yet (unless you demux with libavformat, which contains tons of hacks
+ // that try to determine a PTS).
+ if (!sh->codec->lav_codecpar)
+ avp->video_delay = 16;
+#endif
+
+ if (avp->codec_id == AV_CODEC_ID_NONE)
+ return -1;
+
+ if (avcodec_parameters_copy(rst->av_stream->codecpar, avp) < 0)
+ return -1;
+
+ rst->av_stream->time_base = mp_get_codec_timebase(sh->codec);
+
+ MP_TARRAY_APPEND(priv, priv->streams, priv->num_streams, rst);
+ return 0;
+}
+
+struct mp_recorder *mp_recorder_create(struct mpv_global *global,
+ const char *target_file,
+ struct sh_stream **streams,
+ int num_streams)
+{
+ struct mp_recorder *priv = talloc_zero(NULL, struct mp_recorder);
+
+ priv->global = global;
+ priv->log = mp_log_new(priv, global->log, "recorder");
+
+ if (!num_streams) {
+ MP_ERR(priv, "No streams.\n");
+ goto error;
+ }
+
+ priv->mux = avformat_alloc_context();
+ if (!priv->mux)
+ goto error;
+
+ priv->mux->oformat = av_guess_format(NULL, target_file, NULL);
+ if (!priv->mux->oformat) {
+ MP_ERR(priv, "Output format not found.\n");
+ goto error;
+ }
+
+ if (avio_open2(&priv->mux->pb, target_file, AVIO_FLAG_WRITE, NULL, NULL) < 0) {
+ MP_ERR(priv, "Failed opening output file.\n");
+ goto error;
+ }
+
+ for (int n = 0; n < num_streams; n++) {
+ if (add_stream(priv, streams[n]) < 0) {
+ MP_ERR(priv, "Can't mux one of the input streams.\n");
+ goto error;
+ }
+ }
+
+ // Not sure how to write this in a "standard" way. It appears only mkv
+ // and mp4 support this directly.
+ char version[200];
+ snprintf(version, sizeof(version), "%s experimental stream recording "
+ "feature (can generate broken files - please report bugs)",
+ mpv_version);
+ av_dict_set(&priv->mux->metadata, "encoding_tool", version, 0);
+
+ if (avformat_write_header(priv->mux, NULL) < 0) {
+ MP_ERR(priv, "Write header failed.\n");
+ goto error;
+ }
+
+ priv->opened = true;
+ priv->muxing_from_start = true;
+
+ priv->base_ts = MP_NOPTS_VALUE;
+ priv->rebase_ts = 0;
+
+ MP_WARN(priv, "This is an experimental feature. Output files might be "
+ "broken or not play correctly with various players "
+ "(including mpv itself).\n");
+
+ return priv;
+
+error:
+ mp_recorder_destroy(priv);
+ return NULL;
+}
+
+static void flush_packets(struct mp_recorder *priv)
+{
+ for (int n = 0; n < priv->num_streams; n++) {
+ struct mp_recorder_sink *rst = priv->streams[n];
+ for (int i = 0; i < rst->num_packets; i++)
+ talloc_free(rst->packets[i]);
+ rst->num_packets = 0;
+ }
+}
+
+static void mux_packet(struct mp_recorder_sink *rst,
+ struct demux_packet *pkt)
+{
+ struct mp_recorder *priv = rst->owner;
+ struct demux_packet mpkt = *pkt;
+
+ double diff = priv->rebase_ts - priv->base_ts;
+ mpkt.pts = PTS_ADD(mpkt.pts, diff);
+ mpkt.dts = PTS_ADD(mpkt.dts, diff);
+
+ rst->max_out_pts = MPMAX(rst->max_out_pts, pkt->pts);
+
+ AVPacket avpkt;
+ mp_set_av_packet(&avpkt, &mpkt, &rst->av_stream->time_base);
+
+ avpkt.stream_index = rst->av_stream->index;
+
+ if (avpkt.duration < 0 && rst->sh->type != STREAM_SUB)
+ avpkt.duration = 0;
+
+ AVPacket *new_packet = av_packet_clone(&avpkt);
+ if (!new_packet) {
+ MP_ERR(priv, "Failed to allocate packet.\n");
+ return;
+ }
+
+ if (av_interleaved_write_frame(priv->mux, new_packet) < 0)
+ MP_ERR(priv, "Failed writing packet.\n");
+}
+
+// Write all packets that currently can be written.
+static void mux_packets(struct mp_recorder_sink *rst, bool force)
+{
+ struct mp_recorder *priv = rst->owner;
+ if (!priv->muxing || !rst->num_packets)
+ return;
+
+ int safe_count = 0;
+ for (int n = 0; n < rst->num_packets; n++) {
+ if (rst->packets[n]->keyframe)
+ safe_count = n;
+ }
+ if (force)
+ safe_count = rst->num_packets;
+
+ for (int n = 0; n < safe_count; n++) {
+ mux_packet(rst, rst->packets[n]);
+ talloc_free(rst->packets[n]);
+ }
+
+ // Remove packets[0..safe_count]
+ memmove(&rst->packets[0], &rst->packets[safe_count],
+ (rst->num_packets - safe_count) * sizeof(rst->packets[0]));
+ rst->num_packets -= safe_count;
+}
+
+// If there was a discontinuity, check whether we can resume muxing (and from
+// where).
+static void check_restart(struct mp_recorder *priv)
+{
+ if (priv->muxing)
+ return;
+
+ double min_ts = INFINITY;
+ double rebase_ts = 0;
+ for (int n = 0; n < priv->num_streams; n++) {
+ struct mp_recorder_sink *rst = priv->streams[n];
+ int min_packets = rst->sh->type == STREAM_VIDEO ? QUEUE_MIN_PACKETS : 1;
+
+ rebase_ts = MPMAX(rebase_ts, rst->max_out_pts);
+
+ if (rst->num_packets < min_packets) {
+ if (!rst->proper_eof && rst->sh->type != STREAM_SUB)
+ return;
+ continue;
+ }
+
+ for (int i = 0; i < min_packets; i++)
+ min_ts = MPMIN(min_ts, rst->packets[i]->pts);
+ }
+
+ // Subtitle only stream (wait longer) or stream without any PTS (fuck it).
+ if (!isfinite(min_ts))
+ return;
+
+ priv->rebase_ts = rebase_ts;
+ priv->base_ts = min_ts;
+
+ for (int n = 0; n < priv->num_streams; n++) {
+ struct mp_recorder_sink *rst = priv->streams[n];
+ rst->max_out_pts = min_ts;
+ }
+
+ priv->muxing = true;
+
+ if (!priv->muxing_from_start)
+ MP_WARN(priv, "Discontinuity at timestamp %f.\n", priv->rebase_ts);
+}
+
+void mp_recorder_destroy(struct mp_recorder *priv)
+{
+ if (priv->opened) {
+ for (int n = 0; n < priv->num_streams; n++) {
+ struct mp_recorder_sink *rst = priv->streams[n];
+ if (!rst->proper_eof)
+ continue;
+ mux_packets(rst, true);
+ }
+
+ if (av_write_trailer(priv->mux) < 0)
+ MP_ERR(priv, "Writing trailer failed.\n");
+ }
+
+ if (priv->mux) {
+ if (avio_closep(&priv->mux->pb) < 0)
+ MP_ERR(priv, "Closing file failed\n");
+
+ avformat_free_context(priv->mux);
+ }
+
+ flush_packets(priv);
+ talloc_free(priv);
+}
+
+// This is called on a seek, or when recording was started mid-stream.
+void mp_recorder_mark_discontinuity(struct mp_recorder *priv)
+{
+ flush_packets(priv);
+
+ for (int n = 0; n < priv->num_streams; n++) {
+ struct mp_recorder_sink *rst = priv->streams[n];
+ rst->discont = true;
+ rst->proper_eof = false;
+ }
+
+ priv->muxing = false;
+ priv->muxing_from_start = false;
+}
+
+// Get a stream for writing. The pointer is valid until mp_recorder is
+// destroyed. The stream is the index referencing the stream passed to
+// mp_recorder_create().
+struct mp_recorder_sink *mp_recorder_get_sink(struct mp_recorder *r, int stream)
+{
+ assert(stream >= 0 && stream < r->num_streams);
+ return r->streams[stream];
+}
+
+// Pass a packet to the given stream. The function does not own the packet, but
+// can create a new reference to it if it needs to retain it. Can be NULL to
+// signal proper end of stream.
+void mp_recorder_feed_packet(struct mp_recorder_sink *rst,
+ struct demux_packet *pkt)
+{
+ struct mp_recorder *priv = rst->owner;
+
+ if (!pkt) {
+ rst->proper_eof = true;
+ check_restart(priv);
+ mux_packets(rst, false);
+ return;
+ }
+
+ if (pkt->dts == MP_NOPTS_VALUE && !priv->dts_warning) {
+ // No, FFmpeg has no actually usable helpers to generate correct DTS.
+ // No, FFmpeg doesn't tell us which formats need DTS at all.
+ // No, we can not shut up the FFmpeg warning, which will follow.
+ MP_WARN(priv, "Source stream misses DTS on at least some packets!\n"
+ "If the target file format requires DTS, the written\n"
+ "file will be invalid.\n");
+ priv->dts_warning = true;
+ }
+
+ if (rst->discont && !pkt->keyframe)
+ return;
+ rst->discont = false;
+
+ if (rst->num_packets >= QUEUE_MAX_PACKETS) {
+ MP_ERR(priv, "Stream %d has too many queued packets; dropping.\n",
+ rst->av_stream->index);
+ return;
+ }
+
+ pkt = demux_copy_packet(pkt);
+ if (!pkt)
+ return;
+ MP_TARRAY_APPEND(rst, rst->packets, rst->num_packets, pkt);
+
+ check_restart(priv);
+ mux_packets(rst, false);
+}