[Libav-user] av_parser_parse2 crash

[Brendan Jones]

> Date: Fri, 27 Mar 2015 09:49:35 +0100
> From: nfxjfg at googlemail.com
> To: libav-user at ffmpeg.org
> Subject: Re: [Libav-user] av_parser_parse2 crash
> 
> On Fri, 27 Mar 2015 03:26:58 +0000
> Brendan Jones <brendan55555 at hotmail.com> wrote:
> 
> > Hi,
> >  
> > I am trying to decode my network dvr h264 socket stream directly using av_parser_parse2 but I get a crash when I try to parse the last portion of the buffer I'm passing to the parser. 
> >  
> > For example, if I read 80000 bytes from socket I can parse and then decode most of the data but the last piece passed to av_parser_parse2 causes a crash. 
> >  
> > I have tried different ways to make sure I not trying to pass more than there is in the buffer to the parser.
> >  
> > I'm not very knowledgeable regarding h264 but I suspect it might be because the parser can't parse the last portion of data  due to it wanting more from the socket.
> >  
> > Is there something I can do to avoid this crash ?
> >  
> > Here is my loop just in case it is something I am doing wrong..
> >  
> > int retval;
> > 
> >     uint8_t *inbuf = new uint8_t [20000000];
> > 
> >     int inbuf_start = 0;
> > 
> >     int inbuf_len = 0; 
> > 
> > 
> >     inbuf_start = 0;
> > 
> >     inbuf_len = 0;
> > 
> >     while (socket->waitForReadyRead()) 
> > 
> > 
> >     {
> > 
> >         if(socket->bytesAvailable() > BUFFER_SIZE*2 ) 
> > 
> > 
> >         {
> > 
> >         QByteArray   ba = socket->readAll();
> > 
> >         memcpy(inbuf + inbuf_len, ba.data(), ba.size() );
> > 
> >         inbuf_len += ba.size(); 
> > 
> > 
> > 
> > 
> >         qDebug() << "read bytes in buffer "<<ba.size();
> > 
> >         if (ba.size() == 0) 
> > 
> > 
> >         {
> > 
> >             cerr << "read 0 bytes data." << endl;
> > 
> >             continue; 
> > 
> > 
> >         }
> > 
> > 
> > 
> >         while (inbuf_len) 
> >  
> >  
> >  
> > 
> > 
> >         {
> > 
> >             qDebug() << "before parse total to parse = "<<ba.size();
> > 
> >             qDebug()  << "parsed already "<< inbuf_start;
> > 
> >             qDebug() << "left to parse "<<inbuf_len;
> > 
> >             av_init_packet(&packet2);
> > 
> >             packet2.data = 0;
> > 
> >             packet2.size = 0;
> > 
> >             uint8_t *pout;
> > 
> >             int pout_len;
> > 
> >                 len = av_parser_parse2(parser, c, &pout, &pout_len, 
> > 
> > 
> >                         inbuf + inbuf_start, inbuf_len,
> > 
> >                         AV_NOPTS_VALUE, AV_NOPTS_VALUE, 0); 
> > 
> > 
> > 
> > 
> >             inbuf_start += len;
> > 
> >             inbuf_len -= len;
> > 
> >             packet2.data = pout;
> > 
> >             packet2.size = pout_len;
> > 
> >             if (len) 
> > 
> > 
> >             {
> > 
> >                 retval = avcodec_decode_video2(c, picture, &got_picture, &packet2);
> > 
> >                 if (got_picture && retval > 0) 
> > 
> > 
> >                 {
> > 
> >                    display_frame(c->pix_fmt, picture, screen_pixz,  screen_contextz,  wind,  stride); 
> > 
> > 
> >                    
> > 
> >                 }
> > 
> >             }
> > 
> > 
> > 
> >             av_free_packet(&packet2); 
> > 
> > 
> >         }
> > 
> >         
> > 
> >     }
> > 
> >     }
> >  
> >  
> > Thank you.
> >  
> > Brendan
> >  
> >  		 	   		  
> 
> One thing that immediately comes to mind (though it might not be the
> cause) is that you don't align inbuf. Try allocating it with av_malloc.
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Thanks, I have managed to get the stream kind of working this morning by reading 80000 into buffer from socket and then checking how much is left to parse in the buffer before av_parser_parse2 and if < 10000 then break instead and read some more from socket.
 
I then got an crash reported with something like av_fast_alloc and so after putting a sleep of 1 second each time I loop I don't get a crash no more, but the sleep obviously causes a delay.
 
Is there a proper way to stop this av_fast_alloc crash?

There's not much in examples when using av_parser_parse2 especially regarding network data.
 
Thanks.
 		 	   		  
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