[FFmpeg-user] Detecting I-frames inside a transport stream!!

tadar tadartadar at gmail.com
Thu Sep 12 13:02:43 CEST 2013

Hello, thanks for your suggestion. But I need to do this without using
ffprobe. Probably I found it out but there are some questions in my mind.

I'm finding the key frames that way;

In the adaptation field, I'm getting the Random Access Indicator and if
it's 1, then it's key frame. But there are a lot of packets without
adaptation field.

For instance, I saw a packet with Adaptation Field and Random Access
Indicator is '1'. Does it mean; all the packets after this packet *(until I
see a packet with adaptation field)* belongs to the keyframe?

Thanks a lot

2013/9/12 Stefano Sabatini-2 [via FFmpeg-users] <
ml-node+s933282n4661240h88 at n4.nabble.com>

> On date Monday 2013-09-09 03:56:57 -0700, tadar wrote:
> > Greetings,
> >
> > I am working on Transport Stream. I am writing a C program that breaks
> the
> > payload data(making the bits '0') of the transport stream
> packets(packets of
> > 188 bytes) by the percentage given by the user. But I need to find the
> bytes
> > that belongs to I-frames so that I do not break them.
> >
> > Can anyone please tell me(in detail please), how can I find the
> I-frame's
> > inside an MPEG-4 transport stream file, or is it not possible?
> Tentative approach: you read all packets, select key packets and check
> the pos field. Something you can do with ffprobe -show_packets.
> Note that you could make use of a bitstream filter, make sure to post
> the code for inclusion in case you get something generically useful.
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