How may I free pkt in an ffmpeg write frame method

Question

2.00/5 (2 votes)

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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:

C++

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

radnix

Updated 28-Feb-14 14:55pm

CHill60

v2

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Comments

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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radnix · Answer 1 · 2014-03-04T12:05:00

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:

C#

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&lt;0){
            fprintf(stderr, &quot;%s failed for stream %d, codec %s&quot;,
                    bsfc-&gt;filter-&gt;name, pkt-&gt;stream_index,
                    avctx-&gt;codec ? avctx-&gt;codec-&gt;name : &quot;copy&quot;);
            print_error(&quot;&quot;, 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>

Igor Oleynikov · Answer 2 · 2015-06-04T04:33:00

C++

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);

How may I free pkt in an ffmpeg write frame method

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