【视频开发】关于FFMPEG中内存泄漏的问题之av_bitstream_filter_filter

How may I free pkt in an ffmpeg write frame method

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more: C++ ffmpeg

Greetings

I'm looking at an ffmpeg source code example at :http://svn.perian.org/ffmpeg/ffmpeg.c[^]

In the code, I'm focusing on a method that writes the video frame.

Here is that method:

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static void write_frame(AVFormatContext *s, AVPacket *pkt, AVCodecContext *avctx, AVBitStreamFilterContext *bsfc){
    int ret;
 
    while(bsfc){
        AVPacket new_pkt= *pkt;
        int a= av_bitstream_filter_filter(bsfc, avctx, NULL,
                                          &new_pkt.data, &new_pkt.size,
                                          pkt->data, pkt->size,
                                          pkt->flags & AV_PKT_FLAG_KEY);
        if(a>0){
            av_free_packet(pkt);
            new_pkt.destruct= av_destruct_packet;
        } else if(a<0){
            fprintf(stderr, "%s failed for stream %d, codec %s",
                    bsfc->filter->name, pkt->stream_index,
                    avctx->codec ? avctx->codec->name : "copy");
            print_error("", a);
            if (exit_on_error)
                exit_program(1);
        }
        *pkt= new_pkt;
 
        bsfc= bsfc->next;
    }
 
    ret= av_interleaved_write_frame(s, pkt);
    if(ret < 0){
        print_error("av_interleaved_write_frame()", ret);
        exit_program(1);
    }
}

If I test the code as is, I get a crash at the write "ret= av_interleaved_write_frame(s, pkt);"

But if I comment our the //av_free_packet(pkt);

It works fine, and here is the problem, until after a while, memory grows very very large.

I suspect it's because I've commented out the av_free_packet(pkt)

Any ideas as to why I crash with the original code (with av_free_packet(pkt))?

Posted 28-Feb-14 12:33pm

radnix824

Updated 28-Feb-14 14:55pm

CHill60157.4K

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The_Inventor 2-Mar-14
7:51am

You need to write one frame at a time. Also you are freeing a pointer to what it is that you are trying to write before you write it. Thus it crashes. If you don't free it at all you then keep allocating more and more RAM instead of writing to HDD file, and
freeing memory for next frame.

radnix 4-Mar-14
18:08pm

Thanks ! yes, you've got me thinking.....:)

2 solutions

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Solution 1

Well, I did finally get it working and will post my particular solution here with the hope it may help others. Oh, almost forgot. If you have a suggestion for change to this code, please do:

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static void write_frame(AVFormatContext *s, AVPacket *pkt, AVCodecContext *avctx, AVBitStreamFilterContext *bsfc){
    int ret;
 
    while(bsfc){
        AVPacket new_pkt= *pkt;
        int a= av_bitstream_filter_filter(bsfc, avctx, NULL,
                                          &new_pkt.data, &new_pkt.size,
                                          pkt->data, pkt->size,
                                          pkt->flags & AV_PKT_FLAG_KEY);
        if(a>0){
            //av_free_packet(pkt);//-comment this out

                  if (new_pkt.data != pkt->data)//-added this
                  {
                    av_free_packet(pkt);
 
                    pkt->data = new_pkt.data;
                    pkt->size = new_pkt.size;
 
                    pkt->destruct = av_destruct_packet;
                  }

 

            new_pkt.destruct= av_destruct_packet;
        } else if(a<0){
            fprintf(stderr, "%s failed for stream %d, codec %s",
                    bsfc->filter->name, pkt->stream_index,
                    avctx->codec ? avctx->codec->name : "copy");
            print_error("", a);
            if (exit_on_error)
                exit_program(1);
        }
       <b>// *pkt= new_pkt;//-comment this out</b>

        bsfc= bsfc-&gt;next;
    }
 
    ret= av_interleaved_write_frame(s, pkt);
 
    av_free_packet(pkt);//-added here

    av_bitstream_filter_close(bsfc);//-added here

 

    if(ret &lt; 0){
        print_error(&quot;av_interleaved_write_frame()&quot;, ret);
        exit_program(1);
    }
}</pre>

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Posted 4-Mar-14 12:05pm

radnix824

Comments

The_Inventor 5-Mar-14
6:51am

Looks better. Just remember in a function like this, you need to use your 'dummy' variables correctly. The dummy receives the info, the function operates on the dummy, when the dummy is happy it spits it back in the format you wanted.

radnix 5-Mar-14
18:17pm

Excellent analysis and a pretty good step ahead for future application. The original code is from ffmpeg.c .

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Solution 2

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AVPacket new_pkt = pkt;
int a = av_bitstream_filter_filter(m_bsfDecoderContext, out_stream->codec,
	NULL,
	&new_pkt.data,
				&new_pkt.size,
				pkt.data,
				pkt.size,
				pkt.flags & AV_PKT_FLAG_KEY);
 
			av_free_packet(&pkt);
			pkt.data = new_pkt.data;
			pkt.size = new_pkt.size;
 
			if (av_interleaved_write_frame(ofmt_ctx, &pkt) < 0)break;
			av_free(new_pkt.data);