awesome. So if you open this capture in wireshark and go to preferences
->protocols, type h264, and fill in 96 for dynamic payload types, hit
ok, close and reopen wireshark and this capture file, you'll see that
the udp traffic is decoded as h264.
in this case rtp has fragemented most of the nals. You can see this
when you expand the h264 section of the packet, you'll see an fu
identifier and fu header section. If rtp has fragmented an h264 nal,
you will see an fu identifier of type FU-A or FU-B, followed by an FU
header with bits that indicate whether this is the start of a nal, the
end of a nal, or the middle. FU-A expects nal fragments to be passed
sequentially with no reordering tolerated, so you see how an FU-A
fragment set can be rebuilt. If a nal is fragmented, its REAL nal type
is moved to the FU header type field. nal type 5 is an idr, so consists
of an entire frame. Nal type 1 is a nal that relies on previous nals as
baselines (I mis spoke earlier, I believe that type 1 can rely on any
previous nal, up to the last transmitted type 5)
Sometimes the type 7 and 8 nals (sps and pps) are small enough to be
passed through without being fragmented, and sometimes if they are
repeated in the rtp stream then it can take several seconds for them to
be re-emitted. So watch your own stream and see if the sps and pps nals
are ever emitted. You can make a filter for h264 field types,
h264.nal_unit_type == 5 should show you idr nals, and if you add
h264.start.bit == 1 you should see how often you are receiving a full
frame refresh nal.
Joshua Kordani
LSA Autonomy
On 6/11/14 11:49 AM, Manuel Torres wrote:
Done. I captured just a few seconds to keep the file size low. Here is the
download link:
https://www.wetransfer.com/downloads/8d6c64606d347f395c6a0dfd8702419b20140611154702/5f67e064c7ebf8c694577589d69c1d5420140611154702/c7dee4
On Wed, Jun 11, 2014 at 5:32 PM, Joshua Kordani <[email protected]> wrote:
Can you make a short wireshark capture that includes the rtsp as well as
the rtp traffic going from this camera, for, say, 30 seconds? Do this
using your program to start the feed.
Joshua Kordani
LSA Autonomy
On 6/11/14 11:21 AM, Manuel Torres wrote:
No. It is an external source of which I have no control and I cannot
figure
out what is diferent in it from the rest if the sources I can open with
both avplay and my code. It puzzles me even more that VLC and MPlayer do
open the stream.
Enviado desde dispositivo móvil.
Sent from mobile device.
On Jun 11, 2014 5:15 PM, "Joshua Kordani" <[email protected]> wrote:
Are you creating this stream yourself?
Joshua Kordani
LSA Autonomy
On 6/11/14 11:08 AM, Manuel Torres wrote:
If by "resource" you mean the URL, the answer is no, avplay does not
display the video. The traces in my first e-mail are also displayed by
avplay, that is, no size and no color space.
Enviado desde dispositivo móvil.
Sent from mobile device.
On Jun 11, 2014 4:10 PM, "Luca Barbato" <[email protected]> wrote:
On 11/06/14 09:41, Manuel Torres wrote:
First of all, thank you Luca and Joshua for taking the time to help me
and
thank you very much Joshua for that awesome explanation. I see that
there
is a lot to learn.
Back on topic:
I checked the format context and the codec context and I only found an
empty (NULL) "extradata" field in the codec context. I also checked
some
other fields in both structures where I thought the data could be but
found
nothing. Am I looking in the right place?
Looks quite strange, if you just do avplay rtsp://resource
does it play?
lu
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