[Asterisk-video] several questions to source code of app_h324m
Atle Samuelsen
clona at cyberhouse.no
Thu Jul 26 10:13:33 CDT 2007
Hey Klaus,
I tried this patch with app_mp4.c it does not work as expected to say it
simple :) I get a crash when doing this. a backtrace of the coredump
looks like this:
(gdb) bt
#0 0x001c87a2 in _dl_sysinfo_int80 () from /lib/ld-linux.so.2
#1 0x002087d5 in raise () from /lib/tls/libc.so.6
#2 0x0020a149 in abort () from /lib/tls/libc.so.6
#3 0x0023c40a in __libc_message () from /lib/tls/libc.so.6
#4 0x0024351c in _int_malloc () from /lib/tls/libc.so.6
#5 0x00244f81 in malloc () from /lib/tls/libc.so.6
#6 0x004da969 in MP4Track::ReadSample (this=0xffffffe8,
sampleId=3180576, ppBytes=0x8348f68, pNumBytes=0x8348f6c,
pStartTime=0x0, pDuration=0x0, pRenderingOffset=0x0, pIsSyncSample=0x0)
at mp4util.h:176
#7 0x004dac02 in MP4Track::ReadSampleFragment (this=0x8348f48,
sampleId=2, sampleOffset=2, sampleLength=152, pDest=0x835530a "") at
mp4track.cpp:340
#8 0x004eb5c3 in MP4RtpSampleData::GetData (this=0x83591d0,
pDest=0x835530a "") at mp4property.h:186
#9 0x004e5ad3 in MP4RtpPacket::GetData (this=0x8358da8, pDest=0x835530a
"") at rtphint.cpp:1039
#10 0x004e5d08 in MP4RtpHintTrack::ReadPacket (this=0x8349038,
packetIndex=0, ppBytes=0x83552a8, pNumBytes=0x8355290, ssrc=0,
addHeader=false, addPayload=true) at rtphint.cpp:243
#11 0x004ca978 in MP4File::ReadRtpPacket (this=0x833b930, hintTrackId=4,
packetIndex=0, ppBytes=0x83552a8, pNumBytes=0x8355290, ssrc=0,
includeHeader=false, includePayload=true) at mp4file.cpp:2877
#12 0x004bc623 in MP4ReadRtpPacket (hFile=0x833b930, hintTrackId=4,
packetIndex=0, ppBytes=0x83552a8, pNumBytes=0x8355290, ssrc=0,
includeHeader=false, includePayload=true) at mp4.cpp:2786
#13 0x003cf1ad in mp4_rtp_read (p=0xb79f9de0) at app_mp4.c:256
#14 0x003cfb2c in mp4_play (chan=0x833a6c8, data=0xb79fe030) at
app_mp4.c:511
#15 0x080c6611 in pbx_extension_helper (c=0x833a6c8, con=Variable "con"
is not available.
) at pbx.c:532
#16 0x080c794f in __ast_pbx_run (c=0x833a6c8) at pbx.c:2274
#17 0x080c97fe in pbx_thread (data=0x833a6c8) at pbx.c:2587
#18 0x080f6375 in dummy_start (data=0x6) at utils.c:545
#19 0x0034f341 in start_thread () from /lib/tls/libpthread.so.0
#20 0x002a86fe in clone () from /lib/tls/libc.so.6
(gdb)
Best Regards
Atle
* Klaus Darilion <klaus.mailinglists at pernau.at> [070726 15:26]:
>
>
> Sergio Garcia wrote:
> >
> >
> > ---------- Original Message ---------------------------------- From:
> > Klaus Darilion <klaus.mailinglists at pernau.at> Reply-To: Development
> > discussion of video media support in
> > Asterisk<asterisk-video at lists.digium.com> Date: Wed, 25 Jul 2007
> > 16:10:32 +0200
> >
> >> Hi Sergio!
> >>
> >> I'm reading the code to find out why some things don't work for me.
> >> Can you please comment on my questions?
> >>
> >>
> >> static struct ast_frame* create_ast_frame(void *frame, struct
> >> video_tr *vtr) { int mark = 0; struct ast_frame* send;
> >>
> >> /* Get data & size */ unsigned char * framedata =
> >> FrameGetData(frame); unsigned int framelength =
> >> FrameGetLength(frame);
> >>
> >> /* Depending on the type */ switch(FrameGetType(frame)) { case
> >> MEDIA_AUDIO: /*Check it's AMR */ if
> >> (FrameGetCodec(frame)!=CODEC_AMR) /* exit */ return NULL; /* Create
> >> frame */ send = (struct ast_frame *) malloc(sizeof(struct
> >> ast_frame) + AST_FRIENDLY_OFFSET + framelength + 2);
> >>
> >> If I Understand Correctly (IIUC) you allocate the frame structure
> >> AND the buffer for the data with one malloc. Thus, the frist part
> >> of the allocated memory is the structure, followed by the data
> >> buffer?
> >>
> >> /* Set data*/ send->data = (void*)send + AST_FRIENDLY_OFFSET;
> >>
> >> I think this is wrong - it overwrites the structure. send->data =
> >> (void*)send + sizeof(struct ast_frame) + AST_FRIENDLY_OFFSET;
> >
> > Ups you-'re rigth
>
> Same problem in app_mp4.c static: mp4_rtp_read(struct mp4rtp *p)
>
>
>
> - memset(f, 0, sizeof(struct ast_frame) + 1500);
> + memset(f, 0, sizeof(struct ast_frame) + AST_FRIENDLY_OFFSET + 1500);
> /* Let mp4 lib allocate memory */
> - f->data = (void*)f + AST_FRIENDLY_OFFSET;
> + f->data = (void*)f + sizeof(struct ast_frame) + AST_FRIENDLY_OFFSET;
> + f->offset = AST_FRIENDLY_OFFSET;
> f->datalen = 1500;
>
>
> btw: setting datalen to 1500 is no safe method, as datalen is not
> checked in mpeg4ip library:
>
> > ... The calling application is responsible for ensuring that the
> > buffer is large enough to hold the packet. This can be done by using
> > MP4GetRtpPayload() to retrieve the maximum packet payload size and
> > hence how large the receiving buffer must be. ...
>
> But I could not find the MP4GetRtpPayload() function. :-(
>
> >> send->datalen = framelength; /* Set header cmr */ ((unsigned
> >> char*)(send->data))[0] = 0xF0; /* Set mode */ ((unsigned
> >> char*)(send->data))[1] = (framedata[0] & 0x78) | 0x04;
> >>
> >>
> >> Here you set the Codec Mode Request 2 times? You set the byte 0 to
> >> 0xF0 (what is that - is that something standardized or just a
> >> proprietary method for signaling something?).
> >>
> >> Then you reset the bits 7,2,1,0 and then you set the bit 2. What
> >> for? I though the topmost 4 bits (7,6,5,4) are relevant for the
> >> codec mode?
> >>
> >> /* Copy */ memcpy(send->data+2, framedata, framelength);
> >>
> >> Although the cmr is already copy to framedata[1], it will be copied
> >> (with the original value) to framedata[2] too. Why?
> >
> >
> > What you receive in the framedata is the amr if2 frame, you have to
> > add a 2 byte header for rtp transmision. The problem is that I don't
> > have any softphone client with amr support to test it.. :(
> >
> > See http://www.ietf.org/rfc/rfc3267.txt Chapter 4.4.1. The Payload
> > Header
>
> I have just read RFC 4867 and things are much more clear now.
>
> Thus - what is the exact format how AMR should be encoded in
> ast_frame->data ? Like RFC 4867, octet-aligned, normal order?
>
> >
> >> /* Set video type */ send->frametype = AST_FRAME_VOICE; /* Set
> >> codec value */ send->subclass = AST_FORMAT_AMRNB; /* Rest of
> >> values*/ send->src = "h324m"; wouldn't it be nicer to define
> >> "h324m" as global variable?
> >
> > Ok.
> >
> >> send->samples = 160; send->delivery.tv_usec = 0;
> >> send->delivery.tv_sec = 0; send->mallocd = 0; IIUC setting
> >> mallocd=0 works as the data buffer is allocated together with the
> >> frame structure. Thus it will be freed when to frame structure is
> >> freed.
> >
> >
> > I'll have to check that, probably it's wrong also.
>
> No. I think it is fine. it was just a comment that in this special case
> (allocating the frame structure AND the data buffer with a single
> malloc) it is fine.
>
> regards
> klaus
>
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