[FFmpeg-user] Split video frame accurate respecting GOP's

[belcampo]

On 10/25/2011 04:59 PM, me at renecalles.de wrote:
> Thanks,
>
> i know that from ffprobe but thought it's maybe also implemented in 
> ffmpeg.
>
> The critical part is to pass frame numbers to ffmpeg, as i understand 
> frame accurate seeking is not possible in ffmpeg.
If you read all the posts about that link, you would discover that 
someone, don't remember his name, was so kind to write a small script 
which outputs the key-frame numbers. If your source is 25fps, every 
frame takes .04 seconds.
So if you know that frame# 10021 is a key-frame then you can calculate 
10021*.04 which wil become th value after ffmpeg -ss
>
> Or is there any workaround for that? Another solution could be an 
> option in ffmpeg to split the video every n minutes, but without a 
> script using the -ss and -t options.
AFAIK ffmpeg is not able to do that.
As mentioned earlier tsMuxeR and mkvtoolnix have that ability.
Another option, although time/space intensive is to convert the source 
to an all-keyframes file first, then you can do it frame-accurate.
>
> Best,
> René
>
>
>
> On Tue, 25 Oct 2011 16:33:39 +0200, belcampo wrote:
>> On 10/25/2011 03:48 PM, me at renecalles.de wrote:
>>> Hi Deepika, belcampo,
>>>
>>> thank you both for your input.
>>>
>>> I'm thinking in some kind of more general solution.
>>> The idea is to parse the video, looking for I-Frames in a defined 
>>> interval and split directly before the I-Frame appears.
>>> This could also solve the fixed / non-fixed GOP situation.
>> Search:
>>
>> http://www.google.nl/url?sa=t&rct=j&q=extract%20list%20of%20keyframes%20belcampo&source=web&cd=1&ved=0CBwQFjAA&url=http%3A%2F%2Fffmpeg-users.933282.n4.nabble.com%2FCreating-a-list-of-I-frames-td2299316.html&ei=bcimTojxDc30-gasnN2vCQ&usg=AFQjCNGE63wbQ4bx7TfpJT4fIH_aglfN5w&cad=rja 
>>
>>>
>>> The -ss and -t solution makes me feel a bit uncomfortable as it not 
>>> really "under control".
>>>
>>> Regards,
>>> René
>>>
>>>
>>>
>>> On Tue, 25 Oct 2011 12:49:55 +0200, belcampo wrote:
>>>> On 10/25/2011 11:58 AM, Deepika wrote:
>>>>> Hi rene,
>>>>>
>>>>> Please take a look at -ss and -t options to split the file. If you 
>>>>> have fixed gops at regular intervals this should solve your problem.
>>>>>
>>>>> Regards,
>>>>> Deepika
>>>>> On 10/25/2011 05:04 PM, me at renecalles.de wrote:
>>>>>> Hi there,
>>>>>>
>>>>>> i would like to split video streams frame accurate for separate 
>>>>>> encoding on different machines.
>>>>>>
>>>>>> For that in my theory i need to split those files frame accurate 
>>>>>> respecting the GOP's.
>>>>>>
>>>>>> Now my question is, is there any way to do it with ffmpeg or do i 
>>>>>> have do stick with libav?
>>>>>>
>>>>>> Any hint is appreciated.
>>>> Search for [issue2114] GOP-based multithreading(h264 encoding
>>>> performance boost of 78%)
>>>> I asked for this in june 2010. If your source is as mentioned above
>>>> "you have fixed gops at regular intervals" as with DVB-S mpeg2 files
>>>> which have GOPs of 12-frames it's easy. If it's h264, the HD-channels
>>>> it's more tedious. There is a solution, if you use tsMuxeR/tsMuxerGUI
>>>> you can split the source in parts, where tsMuxeR takes care of
>>>> splitting at GOP-boundaries, each part starts with an I-frame.
>>>> mkvtoolnix has the same ability.
>>>>>>
>>>>>> Thanks a lot.
>>>>>>
>>>>>> René
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>>>>>
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