[Libav-user] Extracted I-Frames seems not correct, Why?

[amir.rouhi at rmit.edu.au]

OMG, when i check the I-Frames by JM software, that software shows only 3
I-Frames. how this is possible? please help me to understand where is my
problem?

On 17 May 2012 12:05, <amir.rouhi at rmit.edu.au> wrote:

> I am confusing guys, i encountered a new problem in regard with adaptive
> and fixed rate I-Frames by ffmpeg under windows. it is as below:
> first i convert the original video (mpeg1) to the pure h.264 format by
> below command for adaptive I-Frame rate:
>
> ffmpeg -i C:\1.mpg -r 25 -an -vcodec libx264 -threads 0  -f h264 -r 25 -g
> 0 C:\1adapt.264  (-g 0 for adaptive I-frame rate)
> ffmpeg -i C:\1.mpg -r 25 -an -vcodec libx264 -threads 0  -f h264 -r 25 -g
> 25 C:\1fixed.264  (-g 25 for fixed I-frame rate every 25 frame one i-frame)
>
> I dont involve you about my first problem which was related to the twice
> tbr value in the h264 transformed videos and their shorter time length
> (with twice faster speed)
>
> my current problem is that when i want to use select filter to extract the
> i-frames from the above 264 videos, it is natural that i expect different
> results and for a 50sec video with -g 25 and 25fps, i expected 50 i-frames
> but the result was exactly same and just 5 frames for both videos. the
> select filter which i used can be seen at below:
>
> ffmpeg -i C:\1adapt.264 -vsync 0 -vf select="eq(pict_type\, PICT_TYPE_I)"
> C:\I-Frm1adapt-%03d.jpeg
> ffmpeg -i C:\1fixed.264 -vsync 0 -vf select="eq(pict_type\, PICT_TYPE_I)"
> C:\I-Frm1fixed-%03d.jpeg
>
> both produce 5 image for a originally 50 sec video with 25fps tbr 25 which
> after transformed reduced to 25 sec with 25fps but tbr 50. Its strange ,
> isnt it?
>
> On 16 May 2012 18:48, Carl Eugen Hoyos <cehoyos at ag.or.at> wrote:
>
>> Alex Cohn <alexcohn at ...> writes:
>>
>> > If I understand correctly, Amir complains about the
>> > encoder, not the decoder.
>>
>> Then your answer was clearly more helpful than mine!
>>
>> Carl Eugen
>>
>> _______________________________________________
>> Libav-user mailing list
>> Libav-user at ffmpeg.org
>> http://ffmpeg.org/mailman/listinfo/libav-user
>>
>
>
>
> --
> Amir H. Rouhi
> PhD Student/ CSIT RMIT University
> Room: 14-09-04
> http://raws.adc.rmit.edu.au/~s3288736/blog2/
>



-- 
Amir H. Rouhi
PhD Student/ CSIT RMIT University
Room: 14-09-04
http://raws.adc.rmit.edu.au/~s3288736/blog2/
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