From 182d3f8221c23716ea4eafa460bdb94968f71f26 Mon Sep 17 00:00:00 2001 From: Anton Khirnov Date: Tue, 24 Jun 2014 10:52:26 +0200 Subject: output example: rewrite encoding logic Properly generate pts for the frames sent to the encoder, avoid using private and deprecated AVStream.pts. --- doc/examples/output.c | 183 +++++++++++++++++++++++++++++--------------------- 1 file changed, 106 insertions(+), 77 deletions(-) (limited to 'doc/examples') diff --git a/doc/examples/output.c b/doc/examples/output.c index d8321be081..7c29df1fdf 100644 --- a/doc/examples/output.c +++ b/doc/examples/output.c @@ -51,6 +51,9 @@ typedef struct OutputStream { AVStream *st; + /* pts of the next frame that will be generated */ + int64_t next_pts; + AVFrame *frame; AVFrame *tmp_frame; @@ -139,57 +142,72 @@ static void open_audio(AVFormatContext *oc, OutputStream *ost) /* Prepare a 16 bit dummy audio frame of 'frame_size' samples and * 'nb_channels' channels. */ -static void get_audio_frame(OutputStream *ost, AVFrame *frame, int nb_channels) +static AVFrame *get_audio_frame(OutputStream *ost) { int j, i, v, ret; - int16_t *q = (int16_t*)frame->data[0]; + int16_t *q = (int16_t*)ost->frame->data[0]; + + /* check if we want to generate more frames */ + if (av_compare_ts(ost->next_pts, ost->st->codec->time_base, + STREAM_DURATION, (AVRational){ 1, 1 }) >= 0) + return NULL; /* when we pass a frame to the encoder, it may keep a reference to it * internally; * make sure we do not overwrite it here */ - ret = av_frame_make_writable(frame); + ret = av_frame_make_writable(ost->frame); if (ret < 0) exit(1); - for (j = 0; j < frame->nb_samples; j++) { + for (j = 0; j < ost->frame->nb_samples; j++) { v = (int)(sin(ost->t) * 10000); - for (i = 0; i < nb_channels; i++) + for (i = 0; i < ost->st->codec->channels; i++) *q++ = v; ost->t += ost->tincr; ost->tincr += ost->tincr2; } + + ost->frame->pts = ost->next_pts; + ost->next_pts += ost->frame->nb_samples; + + return ost->frame; } -static void write_audio_frame(AVFormatContext *oc, OutputStream *ost) +/* + * encode one audio frame and send it to the muxer + * return 1 when encoding is finished, 0 otherwise + */ +static int write_audio_frame(AVFormatContext *oc, OutputStream *ost) { AVCodecContext *c; AVPacket pkt = { 0 }; // data and size must be 0; - int got_packet, ret; + AVFrame *frame; + int got_packet; av_init_packet(&pkt); c = ost->st->codec; - get_audio_frame(ost, ost->frame, c->channels); + frame = get_audio_frame(ost); - avcodec_encode_audio2(c, &pkt, ost->frame, &got_packet); - if (!got_packet) - return; + avcodec_encode_audio2(c, &pkt, frame, &got_packet); - pkt.stream_index = ost->st->index; + if (got_packet) { + pkt.stream_index = ost->st->index; - /* Write the compressed frame to the media file. */ - if (av_interleaved_write_frame(oc, &pkt) != 0) { - fprintf(stderr, "Error while writing audio frame\n"); - exit(1); + /* Write the compressed frame to the media file. */ + if (av_interleaved_write_frame(oc, &pkt) != 0) { + fprintf(stderr, "Error while writing audio frame\n"); + exit(1); + } } + + return (frame || got_packet) ? 0 : 1; } /**************************************************************/ /* video output */ -static int frame_count; - /* Add a video output stream. */ static void add_video_stream(OutputStream *ost, AVFormatContext *oc, enum AVCodecID codec_id) @@ -325,76 +343,99 @@ static void fill_yuv_image(AVFrame *pict, int frame_index, } } -static void write_video_frame(AVFormatContext *oc, OutputStream *ost) +static AVFrame *get_video_frame(OutputStream *ost) { - int ret; - AVCodecContext *c; + AVCodecContext *c = ost->st->codec; - c = ost->st->codec; + /* check if we want to generate more frames */ + if (av_compare_ts(ost->next_pts, ost->st->codec->time_base, + STREAM_DURATION, (AVRational){ 1, 1 }) >= 0) + return NULL; - if (frame_count >= STREAM_NB_FRAMES) { - /* No more frames to compress. The codec has a latency of a few - * frames if using B-frames, so we get the last frames by - * passing the same picture again. */ - } else { - if (c->pix_fmt != AV_PIX_FMT_YUV420P) { - /* as we only generate a YUV420P picture, we must convert it - * to the codec pixel format if needed */ + if (c->pix_fmt != AV_PIX_FMT_YUV420P) { + /* as we only generate a YUV420P picture, we must convert it + * to the codec pixel format if needed */ + if (!ost->sws_ctx) { + ost->sws_ctx = sws_getContext(c->width, c->height, + AV_PIX_FMT_YUV420P, + c->width, c->height, + c->pix_fmt, + SCALE_FLAGS, NULL, NULL, NULL); if (!ost->sws_ctx) { - ost->sws_ctx = sws_getContext(c->width, c->height, - AV_PIX_FMT_YUV420P, - c->width, c->height, - c->pix_fmt, - SCALE_FLAGS, NULL, NULL, NULL); - if (!ost->sws_ctx) { - fprintf(stderr, - "Cannot initialize the conversion context\n"); - exit(1); - } + fprintf(stderr, + "Cannot initialize the conversion context\n"); + exit(1); } - fill_yuv_image(ost->tmp_frame, frame_count, c->width, c->height); - sws_scale(ost->sws_ctx, ost->tmp_frame->data, ost->tmp_frame->linesize, - 0, c->height, ost->frame->data, ost->frame->linesize); - } else { - fill_yuv_image(ost->frame, frame_count, c->width, c->height); } + fill_yuv_image(ost->tmp_frame, ost->next_pts, c->width, c->height); + sws_scale(ost->sws_ctx, ost->tmp_frame->data, ost->tmp_frame->linesize, + 0, c->height, ost->frame->data, ost->frame->linesize); + } else { + fill_yuv_image(ost->frame, ost->next_pts, c->width, c->height); } + ost->frame->pts = ost->next_pts++; + + return ost->frame; +} + +/* + * encode one video frame and send it to the muxer + * return 1 when encoding is finished, 0 otherwise + */ +static int write_video_frame(AVFormatContext *oc, OutputStream *ost) +{ + int ret; + AVCodecContext *c; + AVFrame *frame; + int got_packet = 0; + + c = ost->st->codec; + + frame = get_video_frame(ost); + if (oc->oformat->flags & AVFMT_RAWPICTURE) { - /* Raw video case - the API will change slightly in the near - * future for that. */ + /* a hack to avoid data copy with some raw video muxers */ AVPacket pkt; av_init_packet(&pkt); + if (!frame) + return 1; + pkt.flags |= AV_PKT_FLAG_KEY; pkt.stream_index = ost->st->index; - pkt.data = (uint8_t *)ost->frame; + pkt.data = (uint8_t *)frame; pkt.size = sizeof(AVPicture); + pkt.pts = pkt.dts = frame->pts; + av_packet_rescale_ts(&pkt, c->time_base, ost->st->time_base); + ret = av_interleaved_write_frame(oc, &pkt); } else { AVPacket pkt = { 0 }; - int got_packet; av_init_packet(&pkt); /* encode the image */ - ret = avcodec_encode_video2(c, &pkt, ost->frame, &got_packet); - /* If size is zero, it means the image was buffered. */ - if (!ret && got_packet && pkt.size) { + ret = avcodec_encode_video2(c, &pkt, frame, &got_packet); + if (ret < 0) { + fprintf(stderr, "Error encoding a video frame\n"); + exit(1); + } + + if (got_packet) { av_packet_rescale_ts(&pkt, c->time_base, ost->st->time_base); pkt.stream_index = ost->st->index; /* Write the compressed frame to the media file. */ ret = av_interleaved_write_frame(oc, &pkt); - } else { - ret = 0; } } if (ret != 0) { fprintf(stderr, "Error while writing video frame\n"); exit(1); } - frame_count++; + + return (frame || got_packet) ? 0 : 1; } static void close_stream(AVFormatContext *oc, OutputStream *ost) @@ -414,8 +455,8 @@ int main(int argc, char **argv) const char *filename; AVOutputFormat *fmt; AVFormatContext *oc; - double audio_pts, video_pts; int have_video = 0, have_audio = 0; + int encode_video = 0, encode_audio = 0; int i; /* Initialize libavcodec, and register all codecs and formats. */ @@ -457,10 +498,12 @@ int main(int argc, char **argv) if (fmt->video_codec != AV_CODEC_ID_NONE) { add_video_stream(&video_st, oc, fmt->video_codec); have_video = 1; + encode_video = 1; } if (fmt->audio_codec != AV_CODEC_ID_NONE) { add_audio_stream(&audio_st, oc, fmt->audio_codec); have_audio = 1; + encode_audio = 1; } /* Now that all the parameters are set, we can open the audio and @@ -483,28 +526,14 @@ int main(int argc, char **argv) /* Write the stream header, if any. */ avformat_write_header(oc, NULL); - for (;;) { - /* Compute current audio and video time. */ - if (have_audio) - audio_pts = (double)audio_st.st->pts.val * audio_st.st->time_base.num / audio_st.st->time_base.den; - else - audio_pts = 0.0; - - if (have_video) - video_pts = (double)video_st.st->pts.val * video_st.st->time_base.num / - video_st.st->time_base.den; - else - video_pts = 0.0; - - if ((!have_audio || audio_pts >= STREAM_DURATION) && - (!have_video || video_pts >= STREAM_DURATION)) - break; - - /* write interleaved audio and video frames */ - if (!have_video || (have_video && have_audio && audio_pts < video_pts)) { - write_audio_frame(oc, &audio_st); + while (encode_video || encode_audio) { + /* select the stream to encode */ + if (encode_video && + (!encode_audio || av_compare_ts(video_st.next_pts, video_st.st->codec->time_base, + audio_st.next_pts, audio_st.st->codec->time_base) <= 0)) { + encode_video = !write_video_frame(oc, &video_st); } else { - write_video_frame(oc, &video_st); + encode_audio = !write_audio_frame(oc, &audio_st); } } -- cgit v1.2.3