[FFmpeg-cvslog] output example: rewrite encoding logic
Anton Khirnov
git at videolan.org
Fri Jun 27 01:01:09 CEST 2014
ffmpeg | branch: master | Anton Khirnov <anton at khirnov.net> | Tue Jun 24 10:52:26 2014 +0200| [182d3f8221c23716ea4eafa460bdb94968f71f26] | committer: Anton Khirnov
output example: rewrite encoding logic
Properly generate pts for the frames sent to the encoder, avoid
using private and deprecated AVStream.pts.
> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=182d3f8221c23716ea4eafa460bdb94968f71f26
---
doc/examples/output.c | 183 ++++++++++++++++++++++++++++---------------------
1 file changed, 106 insertions(+), 77 deletions(-)
diff --git a/doc/examples/output.c b/doc/examples/output.c
index d8321be..7c29df1 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);
}
}
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