[Libav-user] PTS values and writing encoded audio and video frames ?

[ashika umanga]

thanks all for the tips,
I noticed that in the "muxing.c" example the "pts" value is only set to the
AVFrame of video stream.Is it possible to do the same for Audio stream?
I am sorry but I dont have clear idea on how to use "pts" .I know for
single stream(video) is it used to arrange the decoded frames in correct
order. (?) . but whats the connection when we consider both audio and video
stream ?



On Thu, Apr 12, 2012 at 4:06 PM, NITIN GOYAL <nitinkumgoyal at gmail.com>wrote:

> I think it is always not necessary have to both audio and video with same
> size. I have seen the videos which are greater in length that audio and
> there was silence at the end of the video.  If there is no silence in the
> end of your video then you need to track the PTS values of the audio
> and check where it got shortened.
>
>
> On Thu, Apr 12, 2012 at 12:28 PM, ashika umanga <umanga.forums at gmail.com>wrote:
>
>> I mean, I used "muxing.c" to generate the OGG file.That means both audio
>> and video stream should have the same length,isnt it ?
>>
>>
>>
>> On Thu, Apr 12, 2012 at 3:31 PM, Gagandeep Bawa <
>> gagandeep.bawa at ironroad.com> wrote:
>>
>>> You have to check your video frame rate. I worked on IPhone recorded
>>> videos files and it varies between 15 to 30.
>>>
>>>
>>> On Thu, Apr 12, 2012 at 11:58 AM, ashika umanga <umanga.forums at gmail.com
>>> > wrote:
>>>
>>>> When I encode an OGG file with Theora+Speex , my video length is longer
>>>> than the audio playback.
>>>> Anytips on this ?
>>>>
>>>> On Thu, Apr 12, 2012 at 2:51 PM, Gagandeep Bawa <
>>>> gagandeep.bawa at ironroad.com> wrote:
>>>>
>>>>> Hi,
>>>>>
>>>>> These PTS and DTS used for sync between audio and video data while
>>>>> encoding and presentation. Check below link for more details.
>>>>>
>>>>> *http://dranger.com/ffmpeg/tutorial05.html*
>>>>>
>>>>> Thanks,
>>>>> Gagan
>>>>>
>>>>> On Thu, Apr 12, 2012 at 11:14 AM, ashika umanga <
>>>>> umanga.forums at gmail.com> wrote:
>>>>>
>>>>>> Greetings all,
>>>>>>
>>>>>> I am writing a wrapper class for video/audio encoding by following
>>>>>> the "muxing.c".
>>>>>> http://ffmpeg.org/doxygen/trunk/muxing_8c-source.html
>>>>>>
>>>>>> I see in the example that before writing frames to the file ,is
>>>>>> checks whether the PTS value of audiostream is
>>>>>> lesser than that of videostream.
>>>>>>
>>>>>> code snippet:
>>>>>>
>>>>>>  if (!video_st || (video_st && audio_st && audio_pts < video_pts)) {
>>>>>>             write_audio_frame(oc, audio_st);
>>>>>>         } else {
>>>>>>             write_video_frame(oc, video_st);
>>>>>>             picture->pts++;
>>>>>>         }
>>>>>>
>>>>>> Can someone explain why this test is done? Whats the connection
>>>>>> between PTS values ?
>>>>>>
>>>>>>
>>>>>>
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>>>>>>
>>>>>
>>>>>
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>>>
>>> --
>>>
>>> Thanks & Regards,
>>> Gagandeep, Tech Lead Mobility
>>>
>>> +91- 7307470044
>>>
>>>
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>>>
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