到目前为止，在使用libav*库将H.264转码到VP8时，我未能获得正确的输出帧速率。我使用FFmpeg源代码中的transcoding.c示例的修改创建了一个功能正常的编码Sintel.2010.720p.mkv as WebM（VP8/Vorbis）。不幸的是，生成的文件是48 fps，与原始文件的24 fps和我试图模拟的ffmpeg命令的输出不同。
我注意到ffprobe为这个和其他H.264视频生成的tbc是fps的两倍，而ffmpeg命令生成的VP8流的tbc是默认的1000。stock transcoding.c示例将解码器的时基复制到编码器AVCodecContext，即1/48。通过gdb运行ffmpeg命令看起来AVCodecContext的时基设置为1/24，但是单独进行此更改只会导致生成的视频以24 fps的速度减慢到持续时间的两倍。
我可以创建一个可用的视频，但帧速率加倍。当输出帧速率为正确的24 fps时，视频平滑，但速度减慢到一半。
这是我对这个例子的修改。
/*
* Copyright (c) 2010 Nicolas George
* Copyright (c) 2011 Stefano Sabatini
* Copyright (c) 2014 Andrey Utkin
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* @file
* API example for demuxing, decoding, filtering, encoding and muxing
* @example doc/examples/transcoding.c
*/
#include <libavcodec/avcodec.h>
#include <libavformat/avformat.h>
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/avcodec.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavutil/opt.h>
#include <libavutil/pixdesc.h>
#define STATS_LOG "stats.log"
static AVFormatContext *ifmt_ctx;
static AVFormatContext *ofmt_ctx;
typedef struct FilteringContext {
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
} FilteringContext;
static FilteringContext *filter_ctx;
static int open_input_file(const char *filename) {
int ret;
unsigned int i;
ifmt_ctx = NULL;
if ((ret = avformat_open_input(&ifmt_ctx, filename, NULL, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open input file\n");
return ret;
}
if ((ret = avformat_find_stream_info(ifmt_ctx, NULL)) < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot find stream information\n");
return ret;
}
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
AVStream *stream;
AVCodecContext *codec_ctx;
stream = ifmt_ctx->streams[i];
codec_ctx = stream->codec;
/* Reencode video & audio and remux subtitles etc. */
if (codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO
|| codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
/* Open decoder */
ret = avcodec_open2(codec_ctx,
avcodec_find_decoder(codec_ctx->codec_id), NULL);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to open decoder for stream #%u\n", i);
return ret;
}
}
}
av_dump_format(ifmt_ctx, 0, filename, 0);
return 0;
}
static int init_output_context(char* filename) {
int ret;
ofmt_ctx = NULL;
avformat_alloc_output_context2(&ofmt_ctx, NULL, NULL, filename);
if (!ofmt_ctx) {
av_log(NULL, AV_LOG_ERROR, "Could not create output context\n");
return AVERROR_UNKNOWN;
}
return 0;
}
static int init_webm_encoders(int audioBitRate, int crf, int videoMaxBitRate, int threads,
char* quality, int speed, int pass, char* stats) {
AVStream *out_stream;
AVStream *in_stream;
AVCodecContext *dec_ctx, *enc_ctx;
AVCodec *encoder;
int ret;
unsigned int i;
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
in_stream = ifmt_ctx->streams[i];
dec_ctx = in_stream->codec;
if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO || dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
AVDictionary *opts = NULL;
if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
encoder = avcodec_find_encoder(AV_CODEC_ID_VP8);
out_stream = avformat_new_stream(ofmt_ctx, encoder);
if (!out_stream) {
av_log(NULL, AV_LOG_ERROR, "Failed allocating output stream\n");
return AVERROR_UNKNOWN;
}
enc_ctx = out_stream->codec;
enc_ctx->height = dec_ctx->height;
enc_ctx->width = dec_ctx->width;
enc_ctx->sample_aspect_ratio = dec_ctx->sample_aspect_ratio;
/* take first format from list of supported formats */
enc_ctx->pix_fmt = encoder->pix_fmts[0];
/* video time_base can be set to whatever is handy and supported by encoder */
enc_ctx->time_base = dec_ctx->time_base;
/* enc_ctx->time_base.num = 1; */
/* enc_ctx->time_base.den = 24; */
enc_ctx->bit_rate = videoMaxBitRate;
enc_ctx->thread_count = threads;
switch (pass) {
case 1:
enc_ctx->flags |= CODEC_FLAG_PASS1;
break;
case 2:
enc_ctx->flags |= CODEC_FLAG_PASS2;
if (stats) {
enc_ctx->stats_in = stats;
}
break;
}
char crfString[3];
snprintf(crfString, 3, "%d", crf);
av_dict_set(&opts, "crf", crfString, 0);
av_dict_set(&opts, "quality", quality, 0);
char speedString[3];
snprintf(speedString, 3, "%d", speed);
av_dict_set(&opts, "speed", speedString, 0);
} else {
encoder = avcodec_find_encoder(AV_CODEC_ID_VORBIS);
out_stream = avformat_new_stream(ofmt_ctx, encoder);
if (!out_stream) {
av_log(NULL, AV_LOG_ERROR, "Failed allocating output stream\n");
return AVERROR_UNKNOWN;
}
/* in_stream = ifmt_ctx->streams[i]; */
/* dec_ctx = in_stream->codec; */
enc_ctx = out_stream->codec;
/* encoder = out_stream->codec->codec; */
enc_ctx->sample_rate = dec_ctx->sample_rate;
enc_ctx->channel_layout = dec_ctx->channel_layout;
enc_ctx->channels = av_get_channel_layout_nb_channels(enc_ctx->channel_layout);
/* take first format from list of supported formats */
enc_ctx->sample_fmt = encoder->sample_fmts[0];
enc_ctx->time_base = (AVRational){1, enc_ctx->sample_rate};
enc_ctx->bit_rate = audioBitRate;
}
/* Open codec with the set options */
ret = avcodec_open2(enc_ctx, encoder, &opts);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot open video encoder for stream #%u\n", i);
return ret;
}
int unused = av_dict_count(opts);
if (unused > 0) {
av_log(NULL, AV_LOG_WARNING, "%d unused options\n", unused);
}
/* } else if (dec_ctx->codec_type == AVMEDIA_TYPE_UNKNOWN) { */
} else {
av_log(NULL, AV_LOG_FATAL, "Elementary stream #%d is of unknown type, cannot proceed\n", i);
return AVERROR_INVALIDDATA;
} /* else { */
/* /\* if this stream must be remuxed *\/ */
/* ret = avcodec_copy_context(ofmt_ctx->streams[i]->codec, */
/* ifmt_ctx->streams[i]->codec); */
/* if (ret < 0) { */
/* av_log(NULL, AV_LOG_ERROR, "Copying stream context failed\n"); */
/* return ret; */
/* } */
/* } */
if (ofmt_ctx->oformat->flags & AVFMT_GLOBALHEADER)
enc_ctx->flags |= CODEC_FLAG_GLOBAL_HEADER;
}
return 0;
}
static int open_output_file(const char *filename) {
int ret;
av_dump_format(ofmt_ctx, 0, filename, 1);
if (!(ofmt_ctx->oformat->flags & AVFMT_NOFILE)) {
ret = avio_open(&ofmt_ctx->pb, filename, AVIO_FLAG_WRITE);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Could not open output file '%s'", filename);
return ret;
}
}
/* init muxer, write output file header */
ret = avformat_write_header(ofmt_ctx, NULL);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error occurred when opening output file\n");
return ret;
}
return 0;
}
static int init_filter(FilteringContext* fctx, AVCodecContext *dec_ctx,
AVCodecContext *enc_ctx, const char *filter_spec) {
char args[512];
int ret = 0;
AVFilter *buffersrc = NULL;
AVFilter *buffersink = NULL;
AVFilterContext *buffersrc_ctx = NULL;
AVFilterContext *buffersink_ctx = NULL;
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
AVFilterGraph *filter_graph = avfilter_graph_alloc();
if (!outputs || !inputs || !filter_graph) {
ret = AVERROR(ENOMEM);
goto end;
}
if (dec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {
buffersrc = avfilter_get_by_name("buffer");
buffersink = avfilter_get_by_name("buffersink");
if (!buffersrc || !buffersink) {
av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
ret = AVERROR_UNKNOWN;
goto end;
}
snprintf(args, sizeof(args),
"video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt,
dec_ctx->time_base.num, dec_ctx->time_base.den,
dec_ctx->sample_aspect_ratio.num,
dec_ctx->sample_aspect_ratio.den);
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");
goto end;
}
ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
NULL, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
goto end;
}
ret = av_opt_set_bin(buffersink_ctx, "pix_fmts",
(uint8_t*)&enc_ctx->pix_fmt, sizeof(enc_ctx->pix_fmt),
AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
goto end;
}
} else if (dec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {
buffersrc = avfilter_get_by_name("abuffer");
buffersink = avfilter_get_by_name("abuffersink");
if (!buffersrc || !buffersink) {
av_log(NULL, AV_LOG_ERROR, "filtering source or sink element not found\n");
ret = AVERROR_UNKNOWN;
goto end;
}
if (!dec_ctx->channel_layout)
dec_ctx->channel_layout =
av_get_default_channel_layout(dec_ctx->channels);
snprintf(args, sizeof(args),
"time_base=%d/%d:sample_rate=%d:sample_fmt=%s:channel_layout=0x%"PRIx64,
dec_ctx->time_base.num, dec_ctx->time_base.den, dec_ctx->sample_rate,
av_get_sample_fmt_name(dec_ctx->sample_fmt),
dec_ctx->channel_layout);
ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",
args, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer source\n");
goto end;
}
ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
NULL, NULL, filter_graph);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot create audio buffer sink\n");
goto end;
}
ret = av_opt_set_bin(buffersink_ctx, "sample_fmts",
(uint8_t*)&enc_ctx->sample_fmt, sizeof(enc_ctx->sample_fmt),
AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output sample format\n");
goto end;
}
ret = av_opt_set_bin(buffersink_ctx, "channel_layouts",
(uint8_t*)&enc_ctx->channel_layout,
sizeof(enc_ctx->channel_layout), AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output channel layout\n");
goto end;
}
ret = av_opt_set_bin(buffersink_ctx, "sample_rates",
(uint8_t*)&enc_ctx->sample_rate, sizeof(enc_ctx->sample_rate),
AV_OPT_SEARCH_CHILDREN);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Cannot set output sample rate\n");
goto end;
}
} else {
ret = AVERROR_UNKNOWN;
goto end;
}
/* Endpoints for the filter graph. */
outputs->name = av_strdup("in");
outputs->filter_ctx = buffersrc_ctx;
outputs->pad_idx = 0;
outputs->next = NULL;
inputs->name = av_strdup("out");
inputs->filter_ctx = buffersink_ctx;
inputs->pad_idx = 0;
inputs->next = NULL;
if (!outputs->name || !inputs->name) {
ret = AVERROR(ENOMEM);
goto end;
}
if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_spec,
&inputs, &outputs, NULL)) < 0)
goto end;
if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
goto end;
/* Fill FilteringContext */
fctx->buffersrc_ctx = buffersrc_ctx;
fctx->buffersink_ctx = buffersink_ctx;
fctx->filter_graph = filter_graph;
end:
avfilter_inout_free(&inputs);
avfilter_inout_free(&outputs);
return ret;
}
static int init_filters(enum AVCodecID audioCodec) {
const char *filter_spec;
unsigned int i;
int ret;
filter_ctx = av_malloc_array(ifmt_ctx->nb_streams, sizeof(*filter_ctx));
if (!filter_ctx)
return AVERROR(ENOMEM);
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
filter_ctx[i].buffersrc_ctx = NULL;
filter_ctx[i].buffersink_ctx = NULL;
filter_ctx[i].filter_graph = NULL;
/* Skip streams that are neither audio nor video */
if (!(ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_AUDIO
|| ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO))
continue;
if (ifmt_ctx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO)
filter_spec = "null"; /* passthrough (dummy) filter for video */
else
/* TODO: make this more general */
if (audioCodec == AV_CODEC_ID_VORBIS) {
filter_spec = "asetnsamples=n=64";
} else {
/* filter_spec = "null"; /\* passthrough (dummy) filter for audio *\/ */
filter_spec = "fps=24";
/* filter_spec = "settb=expr=1/24"; */
}
ret = init_filter(&filter_ctx[i], ifmt_ctx->streams[i]->codec,
ofmt_ctx->streams[i]->codec, filter_spec);
if (ret)
return ret;
}
return 0;
}
static int encode_write_frame(AVFrame *filt_frame, unsigned int stream_index, int *got_frame) {
int ret;
int got_frame_local;
AVPacket enc_pkt;
int (*enc_func)(AVCodecContext *, AVPacket *, const AVFrame *, int *) =
(ifmt_ctx->streams[stream_index]->codec->codec_type ==
AVMEDIA_TYPE_VIDEO) ? avcodec_encode_video2 : avcodec_encode_audio2;
if (!got_frame)
got_frame = &got_frame_local;
/* av_log(NULL, AV_LOG_INFO, "Encoding frame\n"); */
/* encode filtered frame */
enc_pkt.data = NULL;
enc_pkt.size = 0;
av_init_packet(&enc_pkt);
ret = enc_func(ofmt_ctx->streams[stream_index]->codec, &enc_pkt,
filt_frame, got_frame);
av_frame_free(&filt_frame);
if (ret < 0)
return ret;
if (!(*got_frame))
return 0;
/* prepare packet for muxing */
enc_pkt.stream_index = stream_index;
enc_pkt.dts = av_rescale_q_rnd(enc_pkt.dts,
ofmt_ctx->streams[stream_index]->codec->time_base,
ofmt_ctx->streams[stream_index]->time_base,
AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
enc_pkt.pts = av_rescale_q_rnd(enc_pkt.pts,
ofmt_ctx->streams[stream_index]->codec->time_base,
ofmt_ctx->streams[stream_index]->time_base,
AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
enc_pkt.duration = av_rescale_q(enc_pkt.duration,
ofmt_ctx->streams[stream_index]->codec->time_base,
ofmt_ctx->streams[stream_index]->time_base);
/* av_log(NULL, AV_LOG_DEBUG, "Muxing frame\n"); */
/* mux encoded frame */
ret = av_interleaved_write_frame(ofmt_ctx, &enc_pkt);
return ret;
}
static int filter_encode_write_frame(AVFrame *frame, unsigned int stream_index) {
int ret;
AVFrame *filt_frame;
/* av_log(NULL, AV_LOG_INFO, "Pushing decoded frame to filters\n"); */
/* push the decoded frame into the filtergraph */
ret = av_buffersrc_add_frame_flags(filter_ctx[stream_index].buffersrc_ctx,
frame, 0);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
return ret;
}
/* pull filtered frames from the filtergraph */
while (1) {
filt_frame = av_frame_alloc();
if (!filt_frame) {
ret = AVERROR(ENOMEM);
break;
}
/* av_log(NULL, AV_LOG_INFO, "Pulling filtered frame from filters\n"); */
ret = av_buffersink_get_frame(filter_ctx[stream_index].buffersink_ctx,
filt_frame);
if (ret < 0) {
/* if no more frames for output - returns AVERROR(EAGAIN)
* if flushed and no more frames for output - returns AVERROR_EOF
* rewrite retcode to 0 to show it as normal procedure completion
*/
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
ret = 0;
av_frame_free(&filt_frame);
break;
}
filt_frame->pict_type = AV_PICTURE_TYPE_NONE;
ret = encode_write_frame(filt_frame, stream_index, NULL);
if (ret < 0)
break;
}
return ret;
}
static int flush_encoder(unsigned int stream_index) {
int ret;
int got_frame;
if (!(ofmt_ctx->streams[stream_index]->codec->codec->capabilities &
CODEC_CAP_DELAY))
return 0;
while (1) {
av_log(NULL, AV_LOG_INFO, "Flushing stream #%u encoder\n", stream_index);
ret = encode_write_frame(NULL, stream_index, &got_frame);
if (ret < 0)
break;
if (!got_frame)
return 0;
}
return ret;
}
static int transcode() {
int ret;
AVPacket packet = { .data = NULL, .size = 0 };
AVFrame *frame = NULL;
enum AVMediaType type;
unsigned int stream_index;
unsigned int i;
int got_frame;
int (*dec_func)(AVCodecContext *, AVFrame *, int *, const AVPacket *);
/* read all packets */
while (1) {
if ((ret = av_read_frame(ifmt_ctx, &packet)) < 0)
break;
stream_index = packet.stream_index;
type = ifmt_ctx->streams[packet.stream_index]->codec->codec_type;
av_log(NULL, AV_LOG_DEBUG, "Demuxer gave frame of stream_index %u\n",
stream_index);
if (filter_ctx[stream_index].filter_graph) {
av_log(NULL, AV_LOG_DEBUG, "Going to reencode&filter the frame\n");
frame = av_frame_alloc();
if (!frame) {
ret = AVERROR(ENOMEM);
break;
}
packet.dts = av_rescale_q_rnd(packet.dts,
ifmt_ctx->streams[stream_index]->time_base,
ifmt_ctx->streams[stream_index]->codec->time_base,
AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
packet.pts = av_rescale_q_rnd(packet.pts,
ifmt_ctx->streams[stream_index]->time_base,
ifmt_ctx->streams[stream_index]->codec->time_base,
AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
dec_func = (type == AVMEDIA_TYPE_VIDEO) ? avcodec_decode_video2 :
avcodec_decode_audio4;
ret = dec_func(ifmt_ctx->streams[stream_index]->codec, frame,
&got_frame, &packet);
if (ret < 0) {
av_frame_free(&frame);
av_log(NULL, AV_LOG_ERROR, "Decoding failed\n");
break;
}
if (got_frame) {
frame->pts = av_frame_get_best_effort_timestamp(frame);
ret = filter_encode_write_frame(frame, stream_index);
av_frame_free(&frame);
if (ret < 0)
goto end;
} else {
av_frame_free(&frame);
}
} else {
/* remux this frame without reencoding */
packet.dts = av_rescale_q_rnd(packet.dts,
ifmt_ctx->streams[stream_index]->time_base,
ofmt_ctx->streams[stream_index]->time_base,
AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
packet.pts = av_rescale_q_rnd(packet.pts,
ifmt_ctx->streams[stream_index]->time_base,
ofmt_ctx->streams[stream_index]->time_base,
AV_ROUND_NEAR_INF|AV_ROUND_PASS_MINMAX);
ret = av_interleaved_write_frame(ofmt_ctx, &packet);
if (ret < 0)
goto end;
}
av_free_packet(&packet);
}
/* flush filters and encoders */
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
/* flush filter */
if (!filter_ctx[i].filter_graph)
continue;
ret = filter_encode_write_frame(NULL, i);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Flushing filter failed\n");
goto end;
}
/* flush encoder */
ret = flush_encoder(i);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Flushing encoder failed\n");
goto end;
}
}
av_write_trailer(ofmt_ctx);
// Retrieve and store the first instance of codec statistics
// TODO: less naive, deal with multiple instances of statistics
for (i = 0; i < ofmt_ctx->nb_streams; i++) {
AVCodecContext* codec = ofmt_ctx->streams[i]->codec;
if ((codec->flags & CODEC_FLAG_PASS1) && (codec->stats_out)){
FILE* logfile = fopen(STATS_LOG, "wb");
fprintf(logfile, "%s", codec->stats_out);
if (fclose(logfile) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error closing log file.\n");
}
break;
}
}
av_log(NULL, AV_LOG_INFO, "output duration = %" PRId64 "\n", ofmt_ctx->duration);
end:
av_free_packet(&packet);
av_frame_free(&frame);
for (i = 0; i < ifmt_ctx->nb_streams; i++) {
avcodec_close(ifmt_ctx->streams[i]->codec);
if (ofmt_ctx && ofmt_ctx->nb_streams > i && ofmt_ctx->streams[i] && ofmt_ctx->streams[i]->codec)
avcodec_close(ofmt_ctx->streams[i]->codec);
if (filter_ctx && filter_ctx[i].filter_graph)
avfilter_graph_free(&filter_ctx[i].filter_graph);
}
av_free(filter_ctx);
avformat_close_input(&ifmt_ctx);
if (ofmt_ctx && !(ofmt_ctx->oformat->flags & AVFMT_NOFILE))
avio_close(ofmt_ctx->pb);
avformat_free_context(ofmt_ctx);
if (ret < 0)
av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret));
return ret ? 1 : 0;
}
int TranscodeToWebM(char* inputPath, char* outputPath, int audioBitRate, int crf, int videoMaxBitRate, int threads,
char* quality, int speed) {
int ret;
unsigned int pass;
char* stats = NULL;
av_register_all();
avfilter_register_all();
for (pass = 1; pass <= 2; pass++) {
if ((ret = open_input_file(inputPath)) < 0)
goto end;
if ((ret = init_output_context(outputPath)) < 0)
goto end;
if (pass == 2) {
size_t stats_length;
if (cmdutils_read_file(STATS_LOG, &stats, &stats_length) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error reading stats file.\n");
break;
}
}
if ((ret = init_webm_encoders(audioBitRate, crf, videoMaxBitRate, threads, quality, speed, pass, stats)) < 0)
goto end;
if ((ret = open_output_file(outputPath)) < 0)
goto end;
if ((ret = init_filters(AV_CODEC_ID_VORBIS)) < 0)
goto end;
if ((ret = transcode()) < 0)
goto end;
}
if (remove(STATS_LOG) != 0) {
av_log(NULL, AV_LOG_ERROR, "Failed to remove %s\n", STATS_LOG);
}
end:
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error occurred: %s\n", av_err2str(ret));
return ret;
}
return 0;
}
这是我试图模拟的ffmpeg命令的输出。
ffmpeg version N-62301-g59a5384 Copyright (c) 2000-2014 the FFmpeg developers
built on Apr 9 2014 09:58:44 with gcc 4.8.2 (GCC) 20140206 (prerelease)
configuration: --prefix=/opt/ffmpeg --extra-cflags=-I/opt/x264/include --extra-ldflags=-L/opt/x264/lib --extra-libs=-ldl --enable-gpl --enable-nonfree --enable-libfdk-aac --enable-libopus --enable-libvorbis --enable-libvpx --enable-libx264
libavutil 52. 75.100 / 52. 75.100
libavcodec 55. 58.103 / 55. 58.103
libavformat 55. 36.102 / 55. 36.102
libavdevice 55. 11.100 / 55. 11.100
libavfilter 4. 3.100 / 4. 3.100
libswscale 2. 6.100 / 2. 6.100
libswresample 0. 18.100 / 0. 18.100
libpostproc 52. 3.100 / 52. 3.100
Input #0, matroska,webm, from '/mnt/scratch/test_source/Sintel.2010.720p.mkv':
Metadata:
encoder : libebml v1.0.0 + libmatroska v1.0.0
creation_time : 2011-04-24 17:20:33
Duration: 00:14:48.03, start: 0.000000, bitrate: 6071 kb/s
Chapter #0.0: start 0.000000, end 103.125000
Metadata:
title : Chapter 01
Chapter #0.1: start 103.125000, end 148.667000
Metadata:
title : Chapter 02
Chapter #0.2: start 148.667000, end 349.792000
Metadata:
title : Chapter 03
Chapter #0.3: start 349.792000, end 437.208000
Metadata:
title : Chapter 04
Chapter #0.4: start 437.208000, end 472.075000
Metadata:
title : Chapter 05
Chapter #0.5: start 472.075000, end 678.833000
Metadata:
title : Chapter 06
Chapter #0.6: start 678.833000, end 744.083000
Metadata:
title : Chapter 07
Chapter #0.7: start 744.083000, end 888.032000
Metadata:
title : Chapter 08
Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709), 1280x544, SAR 1:1 DAR 40:17, 24 fps, 24 tbr, 1k tbn, 48 tbc
Stream #0:1(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 640 kb/s
Metadata:
title : AC3 5.1 @ 640 Kbps
Stream #0:2(ger): Subtitle: subrip
Stream #0:3(eng): Subtitle: subrip
Stream #0:4(spa): Subtitle: subrip
Stream #0:5(fre): Subtitle: subrip
Stream #0:6(ita): Subtitle: subrip
Stream #0:7(dut): Subtitle: subrip
Stream #0:8(pol): Subtitle: subrip
Stream #0:9(por): Subtitle: subrip
Stream #0:10(rus): Subtitle: subrip
Stream #0:11(vie): Subtitle: subrip
[libvpx @ 0x24b74c0] v1.3.0
Output #0, webm, to '/mnt/scratch/test_out/Sintel.2010.720p.script.webm':
Metadata:
encoder : Lavf55.36.102
Chapter #0.0: start 0.000000, end 103.125000
Metadata:
title : Chapter 01
Chapter #0.1: start 103.125000, end 148.667000
Metadata:
title : Chapter 02
Chapter #0.2: start 148.667000, end 349.792000
Metadata:
title : Chapter 03
Chapter #0.3: start 349.792000, end 437.208000
Metadata:
title : Chapter 04
Chapter #0.4: start 437.208000, end 472.075000
Metadata:
title : Chapter 05
Chapter #0.5: start 472.075000, end 678.833000
Metadata:
title : Chapter 06
Chapter #0.6: start 678.833000, end 744.083000
Metadata:
title : Chapter 07
Chapter #0.7: start 744.083000, end 888.032000
Metadata:
title : Chapter 08
Stream #0:0(eng): Video: vp8 (libvpx), yuv420p, 1280x544 [SAR 1:1 DAR 40:17], q=-1--1, pass 2, 60000 kb/s, 1k tbn, 24 tbc
Stream #0:1(eng): Audio: vorbis (libvorbis), 48000 Hz, 5.1(side), fltp, 384 kb/s
Metadata:
title : AC3 5.1 @ 640 Kbps
Stream mapping:
Stream #0:0 -> #0:0 (h264 -> libvpx)
Stream #0:1 -> #0:1 (ac3 -> libvorbis)
Press [q] to stop, [?] for help
frame=21312 fps= 11 q=0.0 Lsize= 567191kB time=00:14:48.01 bitrate=5232.4kbits/s
video:537377kB audio:29266kB subtitle:0kB other streams:0kB global headers:7kB muxing overhead: 0.096885%
最佳答案
看来您的问题在于转码功能，您需要在输入格式PTS/DTS和输出格式PTS/DTS之间进行av-rescale。
也不要相信把任意的数字放进去，继续从上下文和编解码器中获取你正在做的事情。
我写了一个bit about PTS/DTS here可能对你有用。在您的情况下，尽管您已经有了“正确的”PTS/DTS，但您需要将其转换为输出PTS/DTS。
关于c - 使用libav *将H.264转码为VP8的帧速率不正确，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/23098080/