我想使用ffmpeg api显示裁剪和缩放的帧,我使用GTK + 3作为GUI组件。从this tutorial和ffmpeg examples开始,我可以显示未过滤的帧,但有些不稳定。过滤后的帧根本无法正确显示。它主要产生完全黑色的输出。我怀疑这是由于sws_scale(),但我还没有发现为什么会发生这种情况。
使用"琐事"从ffmpeg示例中显示我可以确认正在裁剪和缩放帧。
运行下面的代码我得到了一堆错误:
[swscaler @ 0x7fb58b025400] bad src image pointers
[swscaler @ 0x7fb58b025400] bad dst image pointers
我也遇到了这个错误:
[swscaler @ 0x7fd05c025600] Warning: data is not aligned! This can lead to a speedloss
我尝试制作一个16位对齐的缓冲区,但它似乎没有对结果产生任何影响。
这就是我解码帧并应用滤镜的方法:
void decode(gpointer args) {
int ret;
AVPacket packet;
AVFrame *frame = av_frame_alloc();
AVFrame *filt_frame = av_frame_alloc();
int got_frame;
if(!frame || !filt_frame) {
perror("Could not allocate frame");
exit(1);
}
/* read all packets */
while (1) {
if ((ret = av_read_frame(fmt_ctx, &packet)) < 0)
break;
if (packet.stream_index == video_stream_index) {
got_frame = 0;
ret = avcodec_decode_video2(dec_ctx, frame, &got_frame, &packet);
if (ret < 0) {
av_log(NULL, AV_LOG_ERROR, "Error decoding video\n");
break;
}
if (got_frame) {
frame->pts = av_frame_get_best_effort_timestamp(frame);
/* push the decoded frame into the filtergraph */
if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
break;
}
/* pull filtered frames from the filtergraph */
while (1) {
ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
break;
if (ret < 0)
goto end;
display_frame2(filt_frame, buffersink_ctx->inputs[0]->time_base);
av_frame_unref(filt_frame);
}
av_frame_unref(frame);
}
}
av_free_packet(&packet);
}
end:
avfilter_graph_free(&filter_graph);
avcodec_close(dec_ctx);
avformat_close_input(&fmt_ctx);
av_frame_free(&frame);
av_frame_free(&filt_frame);
if (ret < 0 && ret != AVERROR_EOF) {
fprintf(stderr, "Error occurred: %s\n", av_err2str(ret));
exit(1);
}
}
这就是我显示帧的方式。
void display_frame2(const AVFrame *frame, AVRational time_base) {
GdkPixbuf *pixbuf;
int64_t delay;
AVFrame *filt;
uint8_t *buffer;
int num_bytes, i;
buffer = NULL;
filt = av_frame_alloc();
num_bytes = avpicture_get_size(PIX_FMT_RGB24, dec_ctx->width, dec_ctx->height);
buffer = (uint8_t *)av_malloc(num_bytes * sizeof(uint8_t));
avpicture_fill((AVPicture *)filt, buffer, PIX_FMT_RGB24, dec_ctx->width, dec_ctx->height);
if (frame->pts != AV_NOPTS_VALUE) {
if (last_pts != AV_NOPTS_VALUE) {
/* sleep roughly the right amount of time;
* usleep is in microseconds, just like AV_TIME_BASE. */
delay = av_rescale_q(frame->pts - last_pts,
time_base, AV_TIME_BASE_Q);
if (delay > 0 && delay < 1000000)
usleep(delay);
}
last_pts = frame->pts;
}
sws_scale( sws_ctx,
(uint8_t const * const *)frame->data,
frame->linesize,
0,
frame->height,
filt->data,
filt->linesize);
pixbuf = gdk_pixbuf_new_from_data( filt->data[0], GDK_COLORSPACE_RGB,
0, 8, dec_ctx->width, dec_ctx->height,
filt->linesize[0], NULL, NULL);
gtk_image_set_from_pixbuf((GtkImage *)image, pixbuf);
free( filt );
free( buffer );
}
编辑: 经过一些思考和实验后,我得到了过滤后的帧,尽管是SDL,而不是GTK +。我使用ffmpeg中的转码示例来查看是否可以使用过滤器重新编码视频,这确实有效。在这个例子中,我基本上改变了过滤器的过滤器,大部分工作已经完成。此时我所做的就是使用SDL显示视频,如危险教程中所示。裁剪过滤器会产生很多伪影,但它至少会显示一些东西。
我还需要做更多的工作,看看它是否适用于GTK +。我没有详细研究上面的程序和转码示例中的程序之间的差异,所以我还没弄清楚为什么我的旧代码不显示过滤帧。这两组代码都使用sws_scale(),但是新代码没有错误,所以这必然意味着某些东西是不同的。一旦我取得更多进展,我会更新这篇文章。
编辑2: 根据@ drahnr的要求,添加了一个应该可用的小型可编辑示例。我没有机会尝试更换GtkPixbuf。
#define _XOPEN_SOURCE 600
#include <libavformat/avformat.h>
#include <libavformat/avio.h>
#include <libavfilter/avfiltergraph.h>
#include <libavfilter/avcodec.h>
#include <libavfilter/buffersink.h>
#include <libavfilter/buffersrc.h>
#include <libavcodec/avcodec.h>
#include <libswscale/swscale.h>
#include <libavutil/avstring.h>
#include <libavutil/time.h>
#include <libavutil/opt.h>
#include <unistd.h>
#include <gtk/gtk.h>
#include <gdk/gdkx.h>
GtkWidget *image;
GtkWidget *window;
struct SwsContext *sws_ctx;
char *filter_descr = "crop=100:100,scale=640:360";
static AVFormatContext *fmt_ctx;
static AVCodecContext *dec_ctx;
AVFilterContext *buffersink_ctx;
AVFilterContext *buffersrc_ctx;
AVFilterGraph *filter_graph;
static int video_stream_index = -1;
static void open_input_file(const char *filename)
{
AVCodec *dec;
avformat_open_input(&fmt_ctx, filename, NULL, NULL);
avformat_find_stream_info(fmt_ctx, NULL);
video_stream_index = av_find_best_stream(fmt_ctx, AVMEDIA_TYPE_VIDEO, -1, -1, &dec, 0);
dec_ctx = fmt_ctx->streams[video_stream_index]->codec;
av_opt_set_int(dec_ctx, "refcounted_frames", 1, 0);
avcodec_open2(dec_ctx, dec, NULL);
}
static void init_filters(const char *filters_descr)
{
char args[512];
AVFilter *buffersrc = avfilter_get_by_name("buffer");
AVFilter *buffersink = avfilter_get_by_name("buffersink");
AVFilterInOut *outputs = avfilter_inout_alloc();
AVFilterInOut *inputs = avfilter_inout_alloc();
AVRational time_base = fmt_ctx->streams[video_stream_index]->time_base;
enum AVPixelFormat pix_fmts[] = { PIX_FMT_RGB24, AV_PIX_FMT_NONE };
filter_graph = avfilter_graph_alloc();
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,
time_base.num, time_base.den,
dec_ctx->sample_aspect_ratio.num, dec_ctx->sample_aspect_ratio.den);
avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in", args, NULL, filter_graph);
avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out", NULL, NULL, filter_graph);
av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts, AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
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;
avfilter_graph_parse_ptr(filter_graph, filters_descr, &inputs, &outputs, NULL);
avfilter_graph_config(filter_graph, NULL);
}
static void display_frame2(const AVFrame *frame, AVRational time_base) {
GdkPixbuf *pixbuf;
AVFrame *filt;
uint8_t *buffer;
int num_bytes;
buffer = NULL;
filt = av_frame_alloc();
num_bytes = avpicture_get_size(PIX_FMT_RGB24, dec_ctx->width, dec_ctx->height);
buffer = (uint8_t *)av_malloc(num_bytes * sizeof(uint8_t));
avpicture_fill((AVPicture *)filt, buffer, PIX_FMT_RGB24, dec_ctx->width, dec_ctx->height);
usleep(33670 / 4);
sws_scale( sws_ctx,
(uint8_t const * const *)frame->data,
frame->linesize,
0,
frame->height,
filt->data,
filt->linesize);
pixbuf = gdk_pixbuf_new_from_data( filt->data[0], GDK_COLORSPACE_RGB,
0, 8, dec_ctx->width, dec_ctx->height,
filt->linesize[0], NULL, NULL);
gtk_image_set_from_pixbuf((GtkImage *)image, pixbuf);
free( filt );
free( buffer );
}
void decode(gpointer args) {
int ret;
AVPacket packet;
AVFrame *frame = av_frame_alloc();
AVFrame *filt_frame = av_frame_alloc();
int got_frame;
while (1) {
av_read_frame(fmt_ctx, &packet);
if (packet.stream_index == video_stream_index) {
got_frame = 0;
avcodec_decode_video2(dec_ctx, frame, &got_frame, &packet);
if (got_frame) {
frame->pts = av_frame_get_best_effort_timestamp(frame);
if (av_buffersrc_add_frame_flags(buffersrc_ctx, frame, AV_BUFFERSRC_FLAG_KEEP_REF) < 0) {
av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
break;
}
while (1) {
ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);
if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
break;
// Display original frame
display_frame2(frame, buffersink_ctx->inputs[0]->time_base);
// Display filtered frame
// display_frame2(filt_frame, buffersink_ctx->inputs[0]->time_base);
av_frame_unref(filt_frame);
}
av_frame_unref(frame);
}
}
av_free_packet(&packet);
}
}
static void realize_cb(GtkWidget *widget, gpointer data) {
GThread *tid;
tid = g_thread_new("video", decode, NULL);
}
static void destroy(GtkWidget *widget, gpointer data) {
gtk_main_quit();
}
int main(int argc, char **argv)
{
av_register_all();
avfilter_register_all();
open_input_file(argv[1]);
init_filters(filter_descr);
sws_ctx = NULL;
sws_ctx = sws_getContext( dec_ctx->width, dec_ctx->height, dec_ctx->pix_fmt, dec_ctx->width, dec_ctx->height,
PIX_FMT_RGB24, SWS_BILINEAR, NULL, NULL, NULL );
av_dump_format( fmt_ctx, 0, argv[1], 0);
gtk_init(&argc, &argv);
window = gtk_window_new( GTK_WINDOW_TOPLEVEL );
g_signal_connect(window, "realize", G_CALLBACK(realize_cb), NULL);
g_signal_connect(window, "destroy", G_CALLBACK(destroy), NULL);
gtk_container_set_border_width(GTK_CONTAINER(window), 10);
image = gtk_image_new();
gtk_widget_show(image);
gtk_container_add(GTK_CONTAINER(window), image);
gtk_widget_show(window);
gtk_main();
return 0;
}
答案 0 :(得分:0)
执行此操作的正确方法是使用cairo_surface_t
和裸机GtkDrawingArea
。获取其大小分配,相应地缩放内容(此处:您的视频帧)。
那你什么时候想画画?当然不像你现在那样。
将它同步到帧时钟,并阅读相应的文档页面(是的,这是有效的,但它会对你有所帮助)https://developer.gnome.org/gdk3/stable/GdkFrameClock.html#gdk-frame-clock-begin-updating
并在准备好显示新帧时安排重绘。
我在上面的程序中看到的主要错误是你从一个不是运行GtkImage *image
的线程的线程访问一个UI元素gtk_main/g_event_loop
,这是不允许的,因为只有一个非常小的子集g/gtk_
调用是线程安全的。其中一个要绕过的是g_idle_add
,它将数据回调到主循环中(在gtk文档中搜索GSource
)。
对于对齐方式,我不知道这里的问题是什么,即使将其与posix_memalign
对齐512
字节 <,我也会收到警告/ p>
编辑:看起来,步幅也必须是16字节的倍数,这是所需的对齐方式。
开始clean draft widget implementation at github,虽然这还没有编译 - 但它仍然非常清楚地概述了这个方法。