正确分配并填充FFmpeg中的帧 [英] Correctly Allocate And Fill Frame In FFmpeg
问题描述
我正在用BGR图像填充Frame
进行编码,并且出现内存泄漏.我想我找到了问题的根源,但它似乎是一个图书馆问题.由于FFmpeg是一个非常成熟的库,因此我认为我在滥用它,我希望得到正确使用方法的指导.
I am filling a Frame
with a BGR image for encoding, and I am getting a memory leak. I think I got to the source of the problem but it appears to be a library issue instead. Since FFmpeg is such a mature library, I think I am misusing it and I would like to be instructed on how to do it correctly.
我正在使用以下方式分配Frame
:
I am allocating a Frame
using:
AVFrame *bgrFrame = av_frame_alloc();
然后我使用以下方法在Frame
中分配图像:
And later I allocate the image in the Frame
using:
av_image_alloc(bgrFrame->data, bgrFrame->linesize, bgrFrame->width, bgrFrame->height, AV_PIX_FMT_BGR24, 32);
然后,我使用以下方法填充分配的图像:
Then I fill the image allocated using:
av_image_fill_pointers(bgrFrame->data, AV_PIX_FMT_BGR24, bgrFrame->height, originalBGRImage.data, bgrFrame->linesize);
originalBGRImage
是OpenCV Mat
的位置.
Where originalBGRImage
is an OpenCV Mat
.
这会导致内存泄漏,很明显,av_image_alloc()
分配了内存,而av_image_fill_pointers()
也在相同的指针上分配了内存(我可以看到bgrFrame->data[0]
在调用之间进行更改).
And this has a memory leak, apparently, av_image_alloc()
allocates memory, and av_image_fill_pointers()
also allocates memory, on the same pointers (I can see bgrFrame->data[0]
changing between calls).
如果我打电话
av_freep(&bgrFrame->data[0]);
在av_image_alloc()
之后就可以了,但是如果在av_image_fill_pointers()
之后调用它,即使bgrFrame->data[0]
不是NULL
,程序也会崩溃,我觉得很好奇.
After av_image_alloc()
, it's fine, but if I call it after av_image_fill_pointers()
, the program crashes, even though bgrFrame->data[0]
is not NULL
, which I find very curious.
正在查看FFmpeg的av_image_alloc()
源代码,我看到它在调用av_image_fill_pointers()
在其中两次,一次分配一个缓冲区buff
....,随后在av_image_fill_pointers()
中源代码,data[0]
被图像指针替代,它是(我认为)内存泄漏的源头,因为data[0]
保留了先前av_image_alloc()
的buf
打电话.
Looking FFmpeg's av_image_alloc()
source code, I see it calls av_image_fill_pointers()
twice inside it, once allocating a buffer buff
....and later in av_image_fill_pointers()
source code, data[0]
is substituted by the image pointer, which is (I think) the source of the memory leak, since data[0]
was holding buf
from the previous av_image_alloc()
call.
这带来了最后一个问题:用图像填充框架的正确方法是什么?.
So this brings the final question: What's the correct way of filling a frame with an image?.
推荐答案
您应该分配一次框架.
AVFrame* alloc_picture(enum PixelFormat pix_fmt, int width, int height)
{
AVFrame *f = avcodec_alloc_frame();
if (!f)
return NULL;
int size = avpicture_get_size(pix_fmt, width, height);
uint8_t *buffer = (uint8_t *) av_malloc(size);
if (!buffer) {
av_free(f);
return NULL;
}
avpicture_fill((AVPicture *)f, buffer, pix_fmt, width, height);
return f;
}
是的,允许强制转换(AVPicture *) https://stackoverflow.com/a/20498359/2079934 .
在后续框架中,您可以写入此框架.由于您的OpenCV原始数据是BGR,并且您需要RGB或YUV,因此可以使用sws_scale
.在我的应用程序中,我垂直镜像:
Yes, the cast (AVPicture*) is allowed https://stackoverflow.com/a/20498359/2079934 .
In subsequent frames, you can write into the this frame. Since your OpenCV raw data is BGR and you need RGB or YUV, you can use sws_scale
. In my application, I mirror vertically:
struct SwsContext* convertCtx = sws_getContext(width, height, PIX_FMT_RGB24, c->width, c->height, c->pix_fmt, SWS_FAST_BILINEAR, NULL, NULL, NULL);
avpicture_fill(&pic_raw, (uint8_t*)pixelBuffer, PIX_FMT_RGB24, width, height);
// flip
pic_raw.data[0] += (height - 1) * pic_raw.linesize[0];
pic_raw.linesize[0] *= -1;
sws_scale(convertCtx, pic_raw.data, pic_raw.linesize, 0, height, f->data, f->linesize);
out_size = avcodec_encode_video(c, outputBuffer, outputBufferSize, f);
(您可以根据需要调整PIX_FMT_RGB24并从cv::Mat
中读取,而无需复制数据.)
(You can adapt PIX_FMT_RGB24 to your needs and read from cv::Mat
without copying data.)
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