transcode_step()在转码过程中对pts、dts、duration的处理

对pts、dts、duration的处理主要集中在两大函数里面
1、process_input()读入数据并处理，放到滤镜里面
2、reap_filters()从滤镜读出数据，处理后写入文件

process_input()中对时间的处理

获取数据包

ret = get_input_packet(ifile, &pkt);
1
1
通过这条语句实际里面调用

return av_read_frame(f->ctx, pkt);
1
1
将读取到的帧放到pkt中。

处理获取的pkt中的时间

//如果pkt.dts或pkt.pts有值，而不是AV_NOPTS_VALUE时，做处理。
/*
ifile->ts_offset在open_input_file函数中有处理，涉及到参数"copyts"、"start_at_zero"、"itsoffset"、"ss"
语句如下。
f->ts_offset = o->input_ts_offset - (copy_ts ? (start_at_zero && ic->start_time != AV_NOPTS_VALUE ? ic->start_time : 0) : timestamp);
如果没有这些设置。f->ts_offset=0
*/
if (pkt.dts != AV_NOPTS_VALUE)
pkt.dts += av_rescale_q(ifile->ts_offset, AV_TIME_BASE_Q, ist->st->time_base);
if (pkt.pts != AV_NOPTS_VALUE)
pkt.pts += av_rescale_q(ifile->ts_offset, AV_TIME_BASE_Q, ist->st->time_base);

//ist->ts_scale在add_input_streams函数中设置
/*
ist->ts_scale = 1.0;//默认是1
MATCH_PER_STREAM_OPT(ts_scale, dbl, ist->ts_scale, ic, st);
涉及到的参数是"itsscale"：解释为"set the input ts scale"
貌似是单位
*/
if (pkt.pts != AV_NOPTS_VALUE)
pkt.pts *= ist->ts_scale;
if (pkt.dts != AV_NOPTS_VALUE)
pkt.dts *= ist->ts_scale;

//做时间基的转行
pkt_dts = av_rescale_q_rnd(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q, (enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
if ((ist->dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO ||
ist->dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) &&
pkt_dts != AV_NOPTS_VALUE && ist->next_dts == AV_NOPTS_VALUE && !copy_ts
&& (is->iformat->flags & AVFMT_TS_DISCONT) && ifile->last_ts != AV_NOPTS_VALUE) {
int64_t delta = pkt_dts - ifile->last_ts;
if (delta < -1LL*dts_delta_threshold*AV_TIME_BASE ||
delta > 1LL*dts_delta_threshold*AV_TIME_BASE){
ifile->ts_offset -= delta;
av_log(NULL, AV_LOG_DEBUG,
"Inter stream timestamp discontinuity %"PRId64", new offset= %"PRId64"\n",
delta, ifile->ts_offset);
pkt.dts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
if (pkt.pts != AV_NOPTS_VALUE)
pkt.pts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
}
}

duration = av_rescale_q(ifile->duration, ifile->time_base, ist->st->time_base);
if (pkt.pts != AV_NOPTS_VALUE) {
pkt.pts += duration;
ist->max_pts = FFMAX(pkt.pts, ist->max_pts);
ist->min_pts = FFMIN(pkt.pts, ist->min_pts);
}

if (pkt.dts != AV_NOPTS_VALUE)
pkt.dts += duration;

pkt_dts = av_rescale_q_rnd(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q, (enum AVRounding)(AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX));
if ((ist->dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO ||
ist->dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) &&
pkt_dts != AV_NOPTS_VALUE && ist->next_dts != AV_NOPTS_VALUE &&
!copy_ts) {
int64_t delta = pkt_dts - ist->next_dts;
if (is->iformat->flags & AVFMT_TS_DISCONT) {
if (delta < -1LL*dts_delta_threshold*AV_TIME_BASE ||
delta > 1LL*dts_delta_threshold*AV_TIME_BASE ||
pkt_dts + AV_TIME_BASE/10 < FFMAX(ist->pts, ist->dts)) {
ifile->ts_offset -= delta;
av_log(NULL, AV_LOG_DEBUG,
"timestamp discontinuity %"PRId64", new offset= %"PRId64"\n",
delta, ifile->ts_offset);
pkt.dts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
if (pkt.pts != AV_NOPTS_VALUE)
pkt.pts -= av_rescale_q(delta, AV_TIME_BASE_Q, ist->st->time_base);
}
} else {
if ( delta < -1LL*dts_error_threshold*AV_TIME_BASE ||
delta > 1LL*dts_error_threshold*AV_TIME_BASE) {
av_log(NULL, AV_LOG_WARNING, "DTS %"PRId64", next:%"PRId64" st:%d invalid dropping\n", pkt.dts, ist->next_dts, pkt.stream_index);
pkt.dts = AV_NOPTS_VALUE;
}
if (pkt.pts != AV_NOPTS_VALUE){
int64_t pkt_pts = av_rescale_q(pkt.pts, ist->st->time_base, AV_TIME_BASE_Q);
delta = pkt_pts - ist->next_dts;
if ( delta < -1LL*dts_error_threshold*AV_TIME_BASE ||
delta > 1LL*dts_error_threshold*AV_TIME_BASE) {
av_log(NULL, AV_LOG_WARNING, "PTS %"PRId64", next:%"PRId64" invalid dropping st:%d\n", pkt.pts, ist->next_dts, pkt.stream_index);
pkt.pts = AV_NOPTS_VALUE;
}
}
}
}

if (pkt.dts != AV_NOPTS_VALUE)
ifile->last_ts = av_rescale_q(pkt.dts, ist->st->time_base, AV_TIME_BASE_Q);
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
如果pkt.dts == AV_NOPTS_VALUE 并且pkt.dts == AV_NOPTS_VALUE，以上这些语句都没有起作用。

之后调用如下语句

process_input_packet(ist, &pkt, 0);
1
1
process_input_packet

/* pkt = NULL means EOF (needed to flush decoder buffers) */
static int process_input_packet(InputStream *ist, const AVPacket *pkt, int no_eof)
{
int ret = 0, i;
int got_output = 0;

AVPacket avpkt;
//如果是文件的第一次读取，就处理
if (!ist->saw_first_ts) {
//有B帧的情况下dts和pts是不同的。
ist->dts = ist->st->avg_frame_rate.num ? - ist->dec_ctx->has_b_frames * AV_TIME_BASE / av_q2d(ist->st->avg_frame_rate) : 0;
ist->pts = 0;
if (pkt && pkt->pts != AV_NOPTS_VALUE && !ist->decoding_needed) {
ist->dts += av_rescale_q(pkt->pts, ist->st->time_base, AV_TIME_BASE_Q);
ist->pts = ist->dts; //unused but better to set it to a value thats not totally wrong
}
ist->saw_first_ts = 1;
}
//此时在ist中dts和pts都是有值的，第一次进来是初始值，之后进来的值
//初始化next_dts和next_pts
if (ist->next_dts == AV_NOPTS_VALUE)
ist->next_dts = ist->dts;
if (ist->next_pts == AV_NOPTS_VALUE)
ist->next_pts = ist->pts;
/*如果pkt为NULL，表示流结束了。给avpkt赋值为此后在调用decode_video()->avcodec_decode_video2()时会将剩余的帧都返回。
在process_input()函数的出错处理里面有调用process_input_packet(ist, NULL, 0);就在此处处理
*/
if (!pkt) {
/* EOF handling */
av_init_packet(&avpkt);
avpkt.data = NULL;
avpkt.size = 0;
goto handle_eof;
} else {
avpkt = *pkt;
}

if (pkt->dts != AV_NOPTS_VALUE) {
ist->next_dts = ist->dts = av_rescale_q(pkt->dts, ist->st->time_base, AV_TIME_BASE_Q);
if (ist->dec_ctx->codec_type != AVMEDIA_TYPE_VIDEO || !ist->decoding_needed)
ist->next_pts = ist->pts = ist->dts;
}

// while we have more to decode or while the decoder did output something on EOF
/*pkt里为视频是为一帧，为音频是可能为多帧。所以要一个循环*/
while (ist->decoding_needed && (avpkt.size > 0 || (!pkt && got_output))) {
int duration;
handle_eof:
//
ist->pts = ist->next_pts;
ist->dts = ist->next_dts;

//没什么用。
if (avpkt.size && avpkt.size != pkt->size &&
!(ist->dec->capabilities & AV_CODEC_CAP_SUBFRAMES)) {
av_log(NULL, ist->showed_multi_packet_warning ? AV_LOG_VERBOSE : AV_LOG_WARNING,
"Multiple frames in a packet from stream %d\n", pkt->stream_index);
ist->showed_multi_packet_warning = 1;
}
//解码一个pkt
switch (ist->dec_ctx->codec_type) {
case AVMEDIA_TYPE_AUDIO:
ret = decode_audio (ist, &avpkt, &got_output);
break;
case AVMEDIA_TYPE_VIDEO:
ret = decode_video (ist, &avpkt, &got_output);
if (avpkt.duration) {
//返回的pkt中已经计算出了时长
duration = av_rescale_q(avpkt.duration, ist->st->time_base, AV_TIME_BASE_Q);
} else if(ist->dec_ctx->framerate.num != 0 && ist->dec_ctx->framerate.den != 0) {
//根据帧率计算时长
int ticks= av_stream_get_parser(ist->st) ? av_stream_get_parser(ist->st)->repeat_pict+1 : ist->dec_ctx->ticks_per_frame;
duration = ((int64_t)AV_TIME_BASE *
ist->dec_ctx->framerate.den * ticks) /
ist->dec_ctx->framerate.num / ist->dec_ctx->ticks_per_frame;
} else
duration = 0;
//dts和pts加时长，就是下一个帧的dts和pts，注意pkt中的都是临时的。只是在解码的时候用，过程当中的时间都保持在ist中。
if(ist->dts != AV_NOPTS_VALUE && duration) {
ist->next_dts += duration;
}else
ist->next_dts = AV_NOPTS_VALUE;

if (got_output)
ist->next_pts += duration; //FIXME the duration is not correct in some cases
break;
case AVMEDIA_TYPE_SUBTITLE:
ret = transcode_subtitles(ist, &avpkt, &got_output);
break;
default:
return -1;
}

if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while decoding stream #%d:%d: %s\n",
ist->file_index, ist->st->index, av_err2str(ret));
if (exit_on_error)
exit_program(1);
break;
}

avpkt.dts=
avpkt.pts= AV_NOPTS_VALUE;

// touch data and size only if not EOF
if (pkt) {
if(ist->dec_ctx->codec_type != AVMEDIA_TYPE_AUDIO)
ret = avpkt.size;
avpkt.data += ret;
avpkt.size -= ret;
}
if (!got_output) {
continue;
}
if (got_output && !pkt)
break;
}
//pkt 传入是NULL时，给滤镜传入EOF信息
/* after flushing, send an EOF on all the filter inputs attached to the stream */
/* except when looping we need to flush but not to send an EOF */
if (!pkt && ist->decoding_needed && !got_output && !no_eof) {
int ret = send_filter_eof(ist);
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Error marking filters as finished\n");
exit_program(1);
}
}

/* handle stream copy */
if (!ist->decoding_needed) {
ist->dts = ist->next_dts;
switch (ist->dec_ctx->codec_type) {
case AVMEDIA_TYPE_AUDIO:
ist->next_dts += ((int64_t)AV_TIME_BASE * ist->dec_ctx->frame_size) /
ist->dec_ctx->sample_rate;
break;
case AVMEDIA_TYPE_VIDEO:
if (ist->framerate.num) {
// TODO: Remove work-around for c99-to-c89 issue 7
AVRational time_base_q = AV_TIME_BASE_Q;
int64_t next_dts = av_rescale_q(ist->next_dts, time_base_q, av_inv_q(ist->framerate));
ist->next_dts = av_rescale_q(next_dts + 1, av_inv_q(ist->framerate), time_base_q);
} else if (pkt->duration) {
ist->next_dts += av_rescale_q(pkt->duration, ist->st->time_base, AV_TIME_BASE_Q);
} else if(ist->dec_ctx->framerate.num != 0) {
int ticks= av_stream_get_parser(ist->st) ? av_stream_get_parser(ist->st)->repeat_pict + 1 : ist->dec_ctx->ticks_per_frame;
ist->next_dts += ((int64_t)AV_TIME_BASE *
ist->dec_ctx->framerate.den * ticks) /
ist->dec_ctx->framerate.num / ist->dec_ctx->ticks_per_frame;
}
break;
}
ist->pts = ist->dts;
ist->next_pts = ist->next_dts;
}
for (i = 0; pkt && i < nb_output_streams; i++) {
OutputStream *ost = output_streams[i];

if (!check_output_constraints(ist, ost) || ost->encoding_needed)
continue;
//如果不需要重新编解码，就走到这里。ost->encoding_needed判断。
do_streamcopy(ist, ost, pkt);
}

return got_output;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
decode_video

针对时间的处理只有一句

pkt->dts = av_rescale_q(ist->dts, AV_TIME_BASE_Q, ist->st->time_base);
1
1
将在ist中保存的dts给pkt中

static int decode_video(InputStream *ist, AVPacket *pkt, int *got_output)
{
AVFrame *decoded_frame, *f;
int i, ret = 0, err = 0, resample_changed;
int64_t best_effort_timestamp;
AVRational *frame_sample_aspect;

if (!ist->decoded_frame && !(ist->decoded_frame = av_frame_alloc()))
return AVERROR(ENOMEM);
if (!ist->filter_frame && !(ist->filter_frame = av_frame_alloc()))
return AVERROR(ENOMEM);
//解码后的帧存放处
decoded_frame = ist->decoded_frame;
//开始给pkt中的时间赋值。只对dts赋值。
pkt->dts = av_rescale_q(ist->dts, AV_TIME_BASE_Q, ist->st->time_base);

update_benchmark(NULL);
//实际的解码函数，got_output不为0表示解码出了帧，解码出的帧放到decoded_frame中。
ret = avcodec_decode_video2(ist->dec_ctx,
decoded_frame, got_output, pkt);
update_benchmark("decode_video %d.%d", ist->file_index, ist->st->index);

// The following line may be required in some cases where there is no parser
// or the parser does not has_b_frames correctly
if (ist->st->codec->has_b_frames < ist->dec_ctx->has_b_frames) {
if (ist->dec_ctx->codec_id == AV_CODEC_ID_H264) {
ist->st->codec->has_b_frames = ist->dec_ctx->has_b_frames;
} else
av_log(ist->dec_ctx, AV_LOG_WARNING,
"has_b_frames is larger in decoder than demuxer %d > %d.\n"
"If you want to help, upload a sample "
"of this file to ftp://upload.ffmpeg.org/incoming/ "
"and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)",
ist->dec_ctx->has_b_frames,
ist->st->codec->has_b_frames);
}
//判断输出结果，涉及到参数"xerror"。
check_decode_result(ist, got_output, ret);
//如果解码返回成功，做个判断，看是否解码后的长宽、像素格式和最初分析的一样，不一样就输出。没啥用
if (*got_output && ret >= 0) {
if (ist->dec_ctx->width != decoded_frame->width ||
ist->dec_ctx->height != decoded_frame->height ||
ist->dec_ctx->pix_fmt != decoded_frame->format) {
av_log(NULL, AV_LOG_DEBUG, "Frame parameters mismatch context %d,%d,%d != %d,%d,%d\n",
decoded_frame->width,
decoded_frame->height,
decoded_frame->format,
ist->dec_ctx->width,
ist->dec_ctx->height,
ist->dec_ctx->pix_fmt);
}
}

if (!*got_output || ret < 0)
return ret;
//对应参数"top"，和场有关
if(ist->top_field_first>=0)
decoded_frame->top_field_first = ist->top_field_first;
//记录解码的帧数
ist->frames_decoded++;
//和硬件相关
if (ist->hwaccel_retrieve_data && decoded_frame->format == ist->hwaccel_pix_fmt) {
err = ist->hwaccel_retrieve_data(ist->dec_ctx, decoded_frame);
if (err < 0)
goto fail;
}
ist->hwaccel_retrieved_pix_fmt = decoded_frame->format;
//此句很重要，是解码计算出的帧时间戳
best_effort_timestamp= av_frame_get_best_effort_timestamp(decoded_frame);
if(best_effort_timestamp != AV_NOPTS_VALUE) {
//ist中的时间单位是AV_TIME_BASE_Q，decoded_frame中的时间单位是ist->st->time_base
int64_t ts = av_rescale_q(decoded_frame->pts = best_effort_timestamp, ist->st->time_base, AV_TIME_BASE_Q);

if (ts != AV_NOPTS_VALUE)
ist->next_pts = ist->pts = ts;
}

if (debug_ts) {
av_log(NULL, AV_LOG_INFO, "decoder -> ist_index:%d type:video "
"frame_pts:%s frame_pts_time:%s best_effort_ts:%"PRId64" best_effort_ts_time:%s keyframe:%d frame_type:%d time_base:%d/%d\n",
ist->st->index, av_ts2str(decoded_frame->pts),
av_ts2timestr(decoded_frame->pts, &ist->st->time_base),
best_effort_timestamp,
av_ts2timestr(best_effort_timestamp, &ist->st->time_base),
decoded_frame->key_frame, decoded_frame->pict_type,
ist->st->time_base.num, ist->st->time_base.den);
}
/*表示视频就一帧。解完这次就不解了。处理音频时就没有这一句。在process_input_packet中会对此值做处理。
如果处理完还有值就需要在解码*/
pkt->size = 0;

if (ist->st->sample_aspect_ratio.num)
decoded_frame->sample_aspect_ratio = ist->st->sample_aspect_ratio;
//判断判断为真，需要重新设置滤镜链表。
resample_changed = ist->resample_width != decoded_frame->width ||
ist->resample_height != decoded_frame->height ||
ist->resample_pix_fmt != decoded_frame->format;
if (resample_changed) {
av_log(NULL, AV_LOG_INFO,
"Input stream #%d:%d frame changed from size:%dx%d fmt:%s to size:%dx%d fmt:%s\n",
ist->file_index, ist->st->index,
ist->resample_width, ist->resample_height, av_get_pix_fmt_name(ist->resample_pix_fmt),
decoded_frame->width, decoded_frame->height, av_get_pix_fmt_name(decoded_frame->format));

ist->resample_width = decoded_frame->width;
ist->resample_height = decoded_frame->height;
ist->resample_pix_fmt = decoded_frame->format;

for (i = 0; i < nb_filtergraphs; i++) {
if (ist_in_filtergraph(filtergraphs[i], ist) && ist->reinit_filters &&
configure_filtergraph(filtergraphs[i]) < 0) {
av_log(NULL, AV_LOG_FATAL, "Error reinitializing filters!\n");
exit_program(1);
}
}
}

frame_sample_aspect= av_opt_ptr(avcodec_get_frame_class(), decoded_frame, "sample_aspect_ratio");
for (i = 0; i < ist->nb_filters; i++) {
if (!frame_sample_aspect->num)
*frame_sample_aspect = ist->st->sample_aspect_ratio;

if (i < ist->nb_filters - 1) {
f = ist->filter_frame;
err = av_frame_ref(f, decoded_frame);
if (err < 0)
break;
} else
f = decoded_frame;
//放到滤镜里面
ret = av_buffersrc_add_frame_flags(ist->filters[i]->filter, f, AV_BUFFERSRC_FLAG_PUSH);
if (ret == AVERROR_EOF) {
ret = 0; /* ignore */
} else if (ret < 0) {
av_log(NULL, AV_LOG_FATAL,
"Failed to inject frame into filter network: %s\n", av_err2str(ret));
exit_program(1);
}
}

fail:
av_frame_unref(ist->filter_frame);
av_frame_unref(decoded_frame);
return err < 0 ? err : ret;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
reap_filters

/**
* Get and encode new output from any of the filtergraphs, without causing
* activity.
*
* @return 0 for success, <0 for severe errors
*/
static int reap_filters(int flush)
{
AVFrame *filtered_frame = NULL;
int i;

/* Reap all buffers present in the buffer sinks */
for (i = 0; i < nb_output_streams; i++) {
OutputStream *ost = output_streams[i];
OutputFile *of = output_files[ost->file_index];
AVFilterContext *filter;
AVCodecContext *enc = ost->enc_ctx;
int ret = 0;

if (!ost->filter)
continue;
filter = ost->filter->filter;

if (!ost->filtered_frame && !(ost->filtered_frame = av_frame_alloc())) {
return AVERROR(ENOMEM);
}
//从滤镜处理后的帧存放在这里
filtered_frame = ost->filtered_frame;

while (1) {
double float_pts = AV_NOPTS_VALUE; // this is identical to filtered_frame.pts but with higher precision
//从滤镜获取帧
ret = av_buffersink_get_frame_flags(filter, filtered_frame,
AV_BUFFERSINK_FLAG_NO_REQUEST);
if (ret < 0) {
if (ret != AVERROR(EAGAIN) && ret != AVERROR_EOF) {
av_log(NULL, AV_LOG_WARNING,
"Error in av_buffersink_get_frame_flags(): %s\n", av_err2str(ret));
} else if (flush && ret == AVERROR_EOF) {
//没有数据了。已经到了滤镜的结束。
if (filter->inputs[0]->type == AVMEDIA_TYPE_VIDEO)
do_video_out(of->ctx, ost, NULL, AV_NOPTS_VALUE);
}
break;
}
//如果设置了此值，获取到的帧丢弃
if (ost->finished) {
av_frame_unref(filtered_frame);
continue;
}
//下面这段不知道啥意思
if (filtered_frame->pts != AV_NOPTS_VALUE) {
int64_t start_time = (of->start_time == AV_NOPTS_VALUE) ? 0 : of->start_time;
AVRational tb = enc->time_base;
int extra_bits = av_clip(29 - av_log2(tb.den), 0, 16);

tb.den <<= extra_bits;
float_pts =
av_rescale_q(filtered_frame->pts, filter->inputs[0]->time_base, tb) -
av_rescale_q(start_time, AV_TIME_BASE_Q, tb);
float_pts /= 1 << extra_bits;
// avoid exact midoints to reduce the chance of rounding differences, this can be removed in case the fps code is changed to work with integers
float_pts += FFSIGN(float_pts) * 1.0 / (1<<17);

filtered_frame->pts =
av_rescale_q(filtered_frame->pts, filter->inputs[0]->time_base, enc->time_base) -
av_rescale_q(start_time, AV_TIME_BASE_Q, enc->time_base);
}
//if (ost->source_index >= 0)
// *filtered_frame= *input_streams[ost->source_index]->decoded_frame; //for me_threshold

switch (filter->inputs[0]->type) {
case AVMEDIA_TYPE_VIDEO:
//设置宽高比
if (!ost->frame_aspect_ratio.num)
enc->sample_aspect_ratio = filtered_frame->sample_aspect_ratio;

if (debug_ts) {
av_log(NULL, AV_LOG_INFO, "filter -> pts:%s pts_time:%s exact:%f time_base:%d/%d\n",
av_ts2str(filtered_frame->pts), av_ts2timestr(filtered_frame->pts, &enc->time_base),
float_pts,
enc->time_base.num, enc->time_base.den);
}
//编码并输出到文件
do_video_out(of->ctx, ost, filtered_frame, float_pts);
break;
case AVMEDIA_TYPE_AUDIO:
if (!(enc->codec->capabilities & AV_CODEC_CAP_PARAM_CHANGE) &&
enc->channels != av_frame_get_channels(filtered_frame)) {
av_log(NULL, AV_LOG_ERROR,
"Audio filter graph output is not normalized and encoder does not support parameter changes\n");
break;
}
do_audio_out(of->ctx, ost, filtered_frame);
break;
default:
// TODO support subtitle filters
av_assert0(0);
}

av_frame_unref(filtered_frame);
}
}

return 0;
}
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
do_video_out

static void do_video_out(AVFormatContext *s,
OutputStream *ost,
AVFrame *next_picture,
double sync_ipts)
{
int ret, format_video_sync;
AVPacket pkt;
AVCodecContext *enc = ost->enc_ctx;
AVCodecContext *mux_enc = ost->st->codec;
int nb_frames, nb0_frames, i;
double delta, delta0;
double duration = 0;
int frame_size = 0;
InputStream *ist = NULL;
AVFilterContext *filter = ost->filter->filter;

if (ost->source_index >= 0)
ist = input_streams[ost->source_index];

if (filter->inputs[0]->frame_rate.num > 0 &&
filter->inputs[0]->frame_rate.den > 0)
duration = 1/(av_q2d(filter->inputs[0]->frame_rate) * av_q2d(enc->time_base));

if(ist && ist->st->start_time != AV_NOPTS_VALUE && ist->st->first_dts != AV_NOPTS_VALUE && ost->frame_rate.num)
duration = FFMIN(duration, 1/(av_q2d(ost->frame_rate) * av_q2d(enc->time_base)));

if (!ost->filters_script &&
!ost->filters &&
next_picture &&
ist &&
lrintf(av_frame_get_pkt_duration(next_picture) * av_q2d(ist->st->time_base) / av_q2d(enc->time_base)) > 0) {
duration = lrintf(av_frame_get_pkt_duration(next_picture) * av_q2d(ist->st->time_base) / av_q2d(enc->time_base));
}

if (!next_picture) {
//end, flushing
nb0_frames = nb_frames = mid_pred(ost->last_nb0_frames[0],
ost->last_nb0_frames[1],
ost->last_nb0_frames[2]);
} else {
delta0 = sync_ipts - ost->sync_opts; // delta0 is the "drift" between the input frame (next_picture) and where it would fall in the output.
delta = delta0 + duration;

/* by default, we output a single frame */
nb0_frames = 0; // tracks the number of times the PREVIOUS frame should be duplicated, mostly for variable framerate (VFR)
nb_frames = 1;

format_video_sync = video_sync_method;
if (format_video_sync == VSYNC_AUTO) {
if(!strcmp(s->oformat->name, "avi")) {
format_video_sync = VSYNC_VFR;
} else
format_video_sync = (s->oformat->flags & AVFMT_VARIABLE_FPS) ? ((s->oformat->flags & AVFMT_NOTIMESTAMPS) ? VSYNC_PASSTHROUGH : VSYNC_VFR) : VSYNC_CFR;
if ( ist
&& format_video_sync == VSYNC_CFR
&& input_files[ist->file_index]->ctx->nb_streams == 1
&& input_files[ist->file_index]->input_ts_offset == 0) {
format_video_sync = VSYNC_VSCFR;
}
if (format_video_sync == VSYNC_CFR && copy_ts) {
format_video_sync = VSYNC_VSCFR;
}
}
ost->is_cfr = (format_video_sync == VSYNC_CFR || format_video_sync == VSYNC_VSCFR);

if (delta0 < 0 &&
delta > 0 &&
format_video_sync != VSYNC_PASSTHROUGH &&
format_video_sync != VSYNC_DROP) {
if (delta0 < -0.6) {
av_log(NULL, AV_LOG_WARNING, "Past duration %f too large\n", -delta0);
} else
av_log(NULL, AV_LOG_DEBUG, "Clipping frame in rate conversion by %f\n", -delta0);
sync_ipts = ost->sync_opts;
duration += delta0;
delta0 = 0;
}

switch (format_video_sync) {
case VSYNC_VSCFR:
if (ost->frame_number == 0 && delta0 >= 0.5) {
av_log(NULL, AV_LOG_DEBUG, "Not duplicating %d initial frames\n", (int)lrintf(delta0));
delta = duration;
delta0 = 0;
ost->sync_opts = lrint(sync_ipts);
}
case VSYNC_CFR:
// FIXME set to 0.5 after we fix some dts/pts bugs like in avidec.c
if (frame_drop_threshold && delta < frame_drop_threshold && ost->frame_number) {
nb_frames = 0;
} else if (delta < -1.1)
nb_frames = 0;
else if (delta > 1.1) {
nb_frames = lrintf(delta);
if (delta0 > 1.1)
nb0_frames = lrintf(delta0 - 0.6);
}
break;
case VSYNC_VFR:
if (delta <= -0.6)
nb_frames = 0;
else if (delta > 0.6)
ost->sync_opts = lrint(sync_ipts);
break;
case VSYNC_DROP:
case VSYNC_PASSTHROUGH:
ost->sync_opts = lrint(sync_ipts);
break;
default:
av_assert0(0);
}
}

nb_frames = FFMIN(nb_frames, ost->max_frames - ost->frame_number);
nb0_frames = FFMIN(nb0_frames, nb_frames);

memmove(ost->last_nb0_frames + 1,
ost->last_nb0_frames,
sizeof(ost->last_nb0_frames[0]) * (FF_ARRAY_ELEMS(ost->last_nb0_frames) - 1));
ost->last_nb0_frames[0] = nb0_frames;

if (nb0_frames == 0 && ost->last_dropped) {
nb_frames_drop++;
av_log(NULL, AV_LOG_VERBOSE,
"*** dropping frame %d from stream %d at ts %"PRId64"\n",
ost->frame_number, ost->st->index, ost->last_frame->pts);
}
if (nb_frames > (nb0_frames && ost->last_dropped)www.huacairen88.cn + (nb_frames > nb0_frames)) {
if (nb_frames > dts_error_threshold * 30) {
av_log(NULL, AV_LOG_ERROR, "%d frame duplication too large, skipping\n", nb_frames - 1);
nb_frames_drop++;
return;
}
nb_frames_dup += nb_frames - (nb0_frames && ost->last_dropped) - (nb_frames > nb0_frames);
av_log(NULL, AV_LOG_VERBOSE, "*** %d dup!\n", nb_frames - 1);
}
ost->last_dropped = nb_frames == nb0_frames && next_picture;

/* duplicates frame if needed */
for (i = 0; i < nb_frames; i++) {
AVFrame *in_picture;
av_init_packet(&pkt);
pkt.data = NULL;
pkt.size = 0;

if (i < nb0_frames && ost->last_ www.feiyunyl.cn frame) {
in_picture = ost->last_frame;
} else
in_picture = next_picture;

if (!in_picture)
return;

in_picture->pts = ost->sync_opts;

#if 1
if (!check_recording_time(ost))
#else
if (ost->frame_number >= ost->max_frames)
#endif
return;

#if FF_API_LAVF_FMT_RAWPICTURE
if (s->oformat->flags & AVFMT_RAWPICTURE &&
enc->codec->id == AV_CODEC_ID_RAWVIDEO) {
/* raw pictures are written as AVPicture structure to
avoid any copies. We support temporarily the older
method. */
if (in_picture->interlaced_frame)
mux_enc->field_order = in_picture->top_field_first ? AV_FIELD_TB:AV_FIELD_BT;
else
mux_enc->field_order = AV_FIELD_PROGRESSIVE;
pkt.data = (uint8_t *)in_picture;
pkt.size = sizeof(AVPicture);
pkt.pts = av_rescale_q(in_picture->pts,www.feihuayl.cn enc->time_base, ost->st->time_base);
pkt.flags |= AV_PKT_FLAG_KEY;

write_frame(s, &pkt, ost);
} else
#endif
{
int got_packet, forced_keyframe = 0;
double pts_time;

if (enc->flags & (AV_CODEC_FLAG_INTERLACED_DCT | AV_CODEC_FLAG_INTERLACED_ME) &&
ost->top_field_first >= 0)
in_picture->top_field_first = !!ost->top_field_first;

if (in_picture->interlaced_frame) {
if (enc->codec->id == AV_CODEC_ID_MJPEG)
mux_enc->field_order = in_picture->www.fsmaxbuy.com/ top_field_first ? AV_FIELD_TT:AV_FIELD_BB;
else
mux_enc->field_order = in_picture->top_field_first ? AV_FIELD_TB:AV_FIELD_BT;
} else
mux_enc->field_order = AV_FIELD_PROGRESSIVE;

in_picture->quality = enc->global_quality;
in_picture->pict_type = 0;

pts_time = in_picture->pts != AV_NOPTS_VALUE ?
in_picture->pts * av_q2d(enc->time_base) : NAN;
if (ost->forced_kf_index < ost->forced_kf_count &&
in_picture->pts >= ost->forced_kf_pts[ost->forced_kf_index]) {
ost->forced_kf_index++;
forced_keyframe = 1;
} else if (ost->forced_keyframes_pexpr) {
double res;
ost->forced_keyframes_expr_const_values[FKF_T] = pts_time;
res = av_expr_eval(ost->forced_keyframes_pexpr,
ost->forced_keyframes_expr_const_values, NULL);
ff_dlog(NULL, "force_key_frame: n:%f n_forced:%f prev_forced_n:%f t:%f prev_forced_t:%f -> res:%f\n",
ost->forced_keyframes_expr_const_values[FKF_N],
ost->forced_keyframes_expr_const_values[FKF_N_FORCED],
ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_N],
ost->forced_keyframes_expr_const_vwww.yunfeizao.cn
www.feiyunfan.cn alues[FKF_T],
ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_T],
res);
if (res) {
forced_keyframe = 1;
ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_N] =
ost->forced_keyframes_expr_const_values[FKF_N];
ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_T] =
ost->forced_keyframes_expr_const_values[FKF_T];
ost->forced_keyframes_expr_const_values[FKF_N_FORCED] += 1;
}

ost->forced_keyframes_expr_const_values[FKF_N] += 1;
} else if ( ost->forced_keyframes
&& !strncmp(ost->forced_keyframes, "source", 6)
&& in_picture->key_frame==1) {
forced_keyframe = 1;
}

if (forced_keyframe) {
in_picture->pict_type = AV_PICTURE_TYPE_I;
av_log(NULL, AV_LOG_DEBUG, "Forced keyframe at time %f\n", pts_time);
}

update_benchmark(NULL);
if (debug_ts) {
av_log(NULL, AV_LOG_INFO, "encoder <- type:video "
"frame_pts:%s frame_pts_time:%s time_base:%d/%d\n",
av_ts2str(in_picture->pts), av_ts2timestr(in_picture->pts, &enc->time_base),
enc->time_base.num, enc->time_base.den);
}

ost->frames_encoded++;

ret = avcodec_encode_video2(enc, &pkt, in_picture, &got_packet);
update_benchmark("encode_video %d.%d", ost->file_index, ost->index);
if (ret < 0) {
av_log(NULL, AV_LOG_FATAL, "Video encoding failed\n");
exit_program(1);
}

if (got_packet) {
if (debug_ts) {
av_log(NULL, AV_LOG_INFO, "encoder -> type:video "
"pkt_pts:%s pkt_pts_time:%s pkt_dts:%s pkt_dts_time:%s\n",
av_ts2str(pkt.pts), av_ts2timestr(pkt.pts, &enc->time_base),
av_ts2str(pkt.dts), av_ts2timestr(pkt.dts, &enc->time_base));
}

if (pkt.pts == AV_NOPTS_VALUE && !(enc->codec->capabilities & AV_CODEC_CAP_DELAY))
pkt.pts = ost->sync_opts;

av_packet_rescale_ts(&pkt, enc->time_base, ost->st->time_base);

if (debug_ts) {
av_log(NULL, AV_LOG_INFO, "encoder -> type:video "
"pkt_pts:%s pkt_pts_time:%s pkt_dts:%s pkt_dts_time:%s\n",
av_ts2str(pkt.pts), av_ts2timestr(pkt.pts, &ost->st->time_base),
av_ts2str(pkt.dts), av_ts2timestr(pkt.dts, &ost->st->time_base));
}

frame_size = pkt.size;
write_frame(s, &pkt, ost);

/* if two pass, output log */
if (ost->logfile && enc->stats_out) {
fprintf(ost->logfile, "%s", enc->stats_out);
}
}
}
ost->sync_opts++;
/*
* For video, number of frames in == number of packets out.
* But there may be reordering, so we can't throw away frames on encoder
* flush, we need to limit them here, before they go into encoder.
*/
ost->frame_number++;

if (vstats_filename && frame_size)
do_video_stats(ost, frame_size);
}

if (!ost->last_frame)
ost->last_frame = av_frame_alloc();
av_frame_unref(ost->last_frame);
if (next_picture && ost->last_frame)
av_frame_ref(ost->last_frame, next_picture);
else
av_frame_free(&ost->last_frame);