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ffmpeg: implement -force_key_frames expression evalution
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@ -552,9 +552,16 @@ Force video tag/fourcc. This is an alias for @code{-tag:v}.
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Show QP histogram
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@item -vbsf @var{bitstream_filter}
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Deprecated see -bsf
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@item -force_key_frames[:@var{stream_specifier}] @var{time}[,@var{time}...] (@emph{output,per-stream})
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@item -force_key_frames[:@var{stream_specifier}] expr:@var{expr} (@emph{output,per-stream})
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Force key frames at the specified timestamps, more precisely at the first
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frames after each specified time.
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If the argument is prefixed with @code{expr:}, the string @var{expr}
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is interpreted like an expression and is evaluated for each frame. A
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key frame is forced in case the evaluation is non-zero.
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If one of the times is "@code{chapters}[@var{delta}]", it is expanded into
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the time of the beginning of all chapters in the file, shifted by
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@var{delta}, expressed as a time in seconds.
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@ -567,6 +574,37 @@ before the beginning of every chapter:
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-force_key_frames 0:05:00,chapters-0.1
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@end example
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The expression in @var{expr} can contain the following constants:
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@table @option
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@item n
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the number of current processed frame, starting from 0
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@item n_forced
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the number of forced frames
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@item prev_forced_n
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the number of the previous forced frame, it is @code{NAN} when no
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keyframe was forced yet
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@item prev_forced_t
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the time of the previous forced frame, it is @code{NAN} when no
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keyframe was forced yet
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@item t
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the time of the current processed frame
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@end table
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For example to force a key frame every 5 seconds, you can specify:
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@example
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-force_key_frames expr:gte(t,n_forced*5)
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@end example
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To force a key frame 5 seconds after the time of the last forced one,
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starting from second 13:
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@example
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-force_key_frames expr:if(isnan(prev_forced_t),gte(t,13),gte(t,prev_forced_t+5))
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@end example
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Note that forcing too many keyframes is very harmful for the lookahead
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algorithms of certain encoders: using fixed-GOP options or similar
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would be more efficient.
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@item -copyinkf[:@var{stream_specifier}] (@emph{output,per-stream})
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When doing stream copy, copy also non-key frames found at the
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beginning.
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65
ffmpeg.c
65
ffmpeg.c
@ -109,6 +109,15 @@ const int program_birth_year = 2000;
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static FILE *vstats_file;
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const char *const forced_keyframes_const_names[] = {
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"n",
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"n_forced",
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"prev_forced_n",
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"prev_forced_t",
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"t",
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NULL
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};
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static void do_video_stats(OutputStream *ost, int frame_size);
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static int64_t getutime(void);
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@ -437,6 +446,7 @@ static void exit_program(void)
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avcodec_free_frame(&output_streams[i]->filtered_frame);
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av_freep(&output_streams[i]->forced_keyframes);
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av_expr_free(output_streams[i]->forced_keyframes_pexpr);
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av_freep(&output_streams[i]->avfilter);
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av_freep(&output_streams[i]->logfile_prefix);
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av_freep(&output_streams[i]);
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@ -873,8 +883,9 @@ static void do_video_out(AVFormatContext *s,
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video_size += pkt.size;
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write_frame(s, &pkt, ost);
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} else {
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int got_packet;
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int got_packet, forced_keyframe = 0;
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AVFrame big_picture;
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double pts_time;
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big_picture = *in_picture;
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/* better than nothing: use input picture interlaced
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@ -898,11 +909,41 @@ static void do_video_out(AVFormatContext *s,
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big_picture.quality = ost->st->codec->global_quality;
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if (!enc->me_threshold)
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big_picture.pict_type = 0;
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pts_time = big_picture.pts != AV_NOPTS_VALUE ?
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big_picture.pts * av_q2d(enc->time_base) : NAN;
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if (ost->forced_kf_index < ost->forced_kf_count &&
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big_picture.pts >= ost->forced_kf_pts[ost->forced_kf_index]) {
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big_picture.pict_type = AV_PICTURE_TYPE_I;
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ost->forced_kf_index++;
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forced_keyframe = 1;
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} else if (ost->forced_keyframes_pexpr) {
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double res;
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ost->forced_keyframes_expr_const_values[FKF_T] = pts_time;
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res = av_expr_eval(ost->forced_keyframes_pexpr,
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ost->forced_keyframes_expr_const_values, NULL);
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av_dlog(NULL, "force_key_frame: n:%f n_forced:%f prev_forced_n:%f t:%f prev_forced_t:%f -> res:%f\n",
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ost->forced_keyframes_expr_const_values[FKF_N],
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ost->forced_keyframes_expr_const_values[FKF_N_FORCED],
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ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_N],
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ost->forced_keyframes_expr_const_values[FKF_T],
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ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_T],
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res);
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if (res) {
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forced_keyframe = 1;
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ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_N] =
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ost->forced_keyframes_expr_const_values[FKF_N];
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ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_T] =
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ost->forced_keyframes_expr_const_values[FKF_T];
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ost->forced_keyframes_expr_const_values[FKF_N_FORCED] += 1;
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}
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ost->forced_keyframes_expr_const_values[FKF_N] += 1;
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}
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if (forced_keyframe) {
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big_picture.pict_type = AV_PICTURE_TYPE_I;
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av_log(NULL, AV_LOG_DEBUG, "Forced keyframe at time %f\n", pts_time);
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}
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update_benchmark(NULL);
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ret = avcodec_encode_video2(enc, &pkt, &big_picture, &got_packet);
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update_benchmark("encode_video %d.%d", ost->file_index, ost->index);
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@ -2272,9 +2313,23 @@ static int transcode_init(void)
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codec->bits_per_raw_sample = frame_bits_per_raw_sample;
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}
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if (ost->forced_keyframes)
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parse_forced_key_frames(ost->forced_keyframes, ost,
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ost->st->codec);
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if (ost->forced_keyframes) {
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if (!strncmp(ost->forced_keyframes, "expr:", 5)) {
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ret = av_expr_parse(&ost->forced_keyframes_pexpr, ost->forced_keyframes+5,
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forced_keyframes_const_names, NULL, NULL, NULL, NULL, 0, NULL);
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if (ret < 0) {
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av_log(NULL, AV_LOG_ERROR,
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"Invalid force_key_frames expression '%s'\n", ost->forced_keyframes+5);
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return ret;
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}
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ost->forced_keyframes_expr_const_values[FKF_N] = 0;
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ost->forced_keyframes_expr_const_values[FKF_N_FORCED] = 0;
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ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_N] = NAN;
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ost->forced_keyframes_expr_const_values[FKF_PREV_FORCED_T] = NAN;
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} else {
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parse_forced_key_frames(ost->forced_keyframes, ost, ost->st->codec);
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}
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}
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break;
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case AVMEDIA_TYPE_SUBTITLE:
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codec->time_base = (AVRational){1, 1000};
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14
ffmpeg.h
14
ffmpeg.h
@ -41,6 +41,7 @@
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#include "libavutil/avutil.h"
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#include "libavutil/dict.h"
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#include "libavutil/eval.h"
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#include "libavutil/fifo.h"
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#include "libavutil/pixfmt.h"
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#include "libavutil/rational.h"
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@ -289,6 +290,17 @@ typedef struct InputFile {
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#endif
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} InputFile;
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enum forced_keyframes_const {
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FKF_N,
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FKF_N_FORCED,
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FKF_PREV_FORCED_N,
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FKF_PREV_FORCED_T,
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FKF_T,
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FKF_NB
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};
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extern const char *const forced_keyframes_const_names[];
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typedef struct OutputStream {
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int file_index; /* file index */
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int index; /* stream index in the output file */
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@ -320,6 +332,8 @@ typedef struct OutputStream {
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int forced_kf_count;
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int forced_kf_index;
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char *forced_keyframes;
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AVExpr *forced_keyframes_pexpr;
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double forced_keyframes_expr_const_values[FKF_NB];
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/* audio only */
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int audio_channels_map[SWR_CH_MAX]; /* list of the channels id to pick from the source stream */
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