[Mp4-tech] H.264 frame rate

[Dave Singer]

At 5:48  +0000 15/08/07, ChenJianjun wrote:
>Thanks,Gary!
>
>The reason I cared about "frame rate" is I am 
>wondering how does decoder know when to output 
>a picture. So it seems that there are three 
>places that can decide when to output a picture:
>1) system-level or application-level that you 
>mentioned,it should be a constant frame rate.

Both RTP and the MP4 file format provide for 
individual timestamps for pictures.
>2) VUI parameter,it will point out frame rate is 
>fixed or non-fixed, and the frame rate value if 
>it is fixed.
>3) Picture timing SEI message semantics(SPEC 
>D.2.2), it can calculate a clocktimestamp for 
>each picture, but the parameter"time_scale" and 
>"num_units_in_tick" derives from 2).
>
>So my new question is what's the relationship 
>between 1),2) and 3)? Can I conclude as follows:
>if 1) exists, 2)and 3) does not exist;

2 and 3 are not needed in those circumstances, 
indeed.  The MP4 file format allows the picture 
timing SEI in the stream, but says that the file 
format level timing over-rides it.
>if 1) does not exist, and if 2) point out a 
>fixed frame rate, then 3) does not eixt;
>if 1) does not exist, and if 2) point out a 
>non-fixed frame rate, then 3) exists.
>
>Thanks!
>
>
>
>Subject: RE: [Mp4-tech] H.264 frame rate
>Date: Tue, 14 Aug 2023 10:58:22 -0700
>From: garysull windows.microsoft.com
>To: cjj730 hotmail.com; mp4-tech lists.mpegif.org
>
>.ExternalClass P 
>{padding-right:0px;padding-left:0px;padding-bottom:0px;padding-top:0px;} 
>.ExternalClass 
>{font-size:9pt;font-family:Tahoma;}
>Please define the term frame rate.  Are you 
>under the impression that the number of decoded 
>pictures per second needs to be a constant?  If 
>so, that is an incorrect impression in some use 
>cases.
>
>If there is no frame rate expressed in the video 
>elementary stream syntax, there may be such an 
>animal defined in a system-level or 
>application-level specification.
>
>If there isn't, then it is possible that the 
>video bitstream does not have a frame rate 
>(depending on your definition of what a frame 
>rate is).
>
>However, there will be a constraint on how close 
>together in time the decoder can be required to 
>decode each pair of consecutive pictures in the 
>bitstream in decoding order.  Similarly there 
>will be a constraint on how close together in 
>time the decoder can be required to output each 
>pair of consecutive pictures in the bitstream in 
>output order.  Those constraints are specified 
>by the level constraints in Annex A.
>
>Best Regards,
>
>Gary Sullivan
>
>
>From: mp4-tech-bounces lists.mpegif.org 
>[mailto:mp4-tech-bounces lists.mpegif.org] On 
>Behalf Of ChenJianjun
>Sent: Tuesday, August 14, 2023 5:41 AM
>To: mp4-tech lists.mpegif.org
>Subject: [Mp4-tech] H.264 frame rate
>
>Dear experts:
>
>How to calculate the H.264 frame rate?
>I noted that VUI parameter(SPEC E.1) and Picture 
>timing SEI message semantics(SPEC D.2.2) may 
>have such information.But they are optional,then 
>how to get the frame rate information if there's 
>no such information?
>
>Thanks!
>
>
>í ¼› Windows Live Spaces 
>ó^ï¸óF«·èºã§ãù±zìIêäàÅB 
><http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mkt=zh-cn>óß분¢ 'ÅI
>
>
>
>í ¼› Windows Live Spaces 
>ó^ï¸óF«·èºã§ãù±zìIêäàÅB 
><http://spaces.live.com/spacesapi.aspx?wx_action=create&wx_url=/friends.aspx&mkt=zh-cn>óß분¢ 'ÅI
>
>_______________________________________________
>NOTE: Please use clear subject lines for your 
>posts. Include [audio, [video], [systems], 
>[general] or another apppropriate identifier to 
>indicate the type of question you have.
>
>Note: Conduct on the mailing list is subject to 
>the Antitrust guidelines found at 
>http://www.mpegif.org/public/documents/vault/mp-out-30042-Antitrust.php

-- 
David Singer
Apple/QuickTime
-------------- next part --------------
An HTML attachment was scrubbed...
URL: /pipermail/mp4-tech/attachments/20070817/25a600c3/attachment.html