[Asterisk-video] several questions to source code of app_h324m
Klaus Darilion
klaus.mailinglists at pernau.at
Fri Jul 27 04:09:23 CDT 2007
which audio codec?
which video codec?
Atle Samuelsen wrote:
> * Klaus Darilion <klaus.mailinglists at pernau.at> [070727 09:21]:
>> What scenario do you use? SIP<->mp4play or h324m_gw<->mp4play or ....?
>
> Hi Klaus,
>
> I used sip-> mp4play
>
> My extentions conf looks somewhat like this:
> exten => 1,1,answer()
> exten => 1,n,mp4play(/tmp/test.mp4)
> exten => 1,n,mp4save(/tmp/test.mp4)
>
> The test.mp4 is recorded with mp4save()
> -A
>> Atle Samuelsen wrote:
>>> 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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