[FFmpeg-user] RTSP stream fps 29.97 instead of 30

[Carl Eugen Hoyos]

2017-10-04 23:20 GMT+02:00 Mark Thompson <sw at jkqxz.net>:
> On 03/10/17 21:22, Jonathan Viney wrote:
>> On Tue, Oct 3, 2017 at 1:56 PM, Mark Thompson <sw at jkqxz.net> wrote:
>>
>>> On 03/10/17 00:56, Jonathan Viney wrote:

>>> parameter-sets=Z2QAM6w0yAPABD/8BbgICAoAAAfSAAHUwdDAAGP/
>>> gAAMf+Nd5caGAAMf/AAAY/8a7y4b04A=,aO48MA==
>>>
>>> This SPS in the SDP decodes with:
>>>
>>> @126   VUI: timing_info_present_flag                                 1 (
>>> 1)
>>> @127   VUI: num_units_in_tick
>>> 00000000000000000000001111101001 (1001)
>>> @159   VUI: time_scale
>>>  00000000000000001110101001100000 (60000)
>>> @191   VUI: fixed_frame_rate_flag                                    1 (
>>> 1)
>>>
>>> That is, the H.264 stream indeed has a fixed framerate of 60000/1001/2 ~
>>> 29.97fps, and that is what ffmpeg is reading - the RTSP layer is likely
>>> lying about it.  (You may be able to count frames to check that.)
>>>
>>> If you want an exactly 30fps output then you should tell the camera to
>>> generate a 30fps stream rather than the 30000/1001fps it currently is.

>> Thanks Mark. That's interesting, I'll see if there is a way to adjust the
>> stream from the camera.
>>
>> How did you decode the data from the sprop-parameter-sets value?
>
> It's just the SPS and PPS base64 coded: decode the base64,
> add start codes, feed it to any H.264 stream parser.

My question would have been:
Where can I find any H.264 stream parser?

Thank you, Carl Eugen