[Mp4-tech] Synchronizing MP4 files from multiple sources
Dave Singer
singer apple.com
Tue Jan 15 11:45:33 EST 2008
At 16:31 -0500 14/01/08, bobsadur aol.com wrote:
>I've got several video recorders recording MP4 at the same time. I
>have an accurate common clock going to each recorder, so the access
>unit durations should be consistent between recordings. What I
>don't control is the record button on each recorder. They can be
>pressed at different times, and in some cases a recording will be
>made on one recorder but not the others. Where there is overlap,
>though, I want to show the video synchronized on the same display.
>Any advice about how to set this up? I thought of having an OCR
>stream in each file, but I read that it's uncommon to use that with
>stored files, as it's meant to correct for network delays. I've
>thought of creating another file with a BIFS stream that refers to
>the separate recordings, introducing each one as data is available.
>Any other suggestions?
I would have thought that a timecode track (quicktime style, or maybe
something else) would be what you need, wouldn't it?
>
>Bob Sadur
>
>
>
>
>-----Original Message-----
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>Subject: Mp4-tech Digest, Vol 54, Issue 4
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>Today's Topics:
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> 1. question about mb_in_video_packet (Matthew)
> 2. Corresponding block predictor in Reference frame in JM 12.2
> ME Algorithms (Peace)
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>----------------------------------------------------------------------
>
>Message: 1
>Date: Sun, 13 Jan 2024 17:26:00 -0800
>From: "Matthew"
><<mailto:kingshine.matthew gmail.com>kingshine.matthew gmail.com>
>Subject: [Mp4-tech] question about mb_in_video_packet
>To: <<mailto:Mp4-tech lists.mpegif.org>Mp4-tech lists.mpegif.org>
>Message-ID: <003a01c8564c$7519afa0$d332a8c0 MatthewWang>
>Content-Type: text/plain; charset="iso-8859-1"
>
>Hi, Dear all
>
>
>
>In the MPEG-4 video syntax, "data_partitioned_i_vop"
>
>There is a element "mb_in_video_packet", I don't know where this
>element can be
>obtained,
>
>Is it in the system syntax or I can't compute it through other
>syntax elelments.
>
>
>Thanks
>
>Matthew
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>------------------------------
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>Message: 2
>Date: Mon, 14 Jan 2024 18:11:41 +0900
>From: Peace <<mailto:humaira.nisar gmail.com>humaira.nisar gmail.com>
>Subject: [Mp4-tech] Corresponding block predictor in Reference frame
> in JM 12.2 ME Algorithms
>To: <mailto:mp4-tech lists.mpegif.org>mp4-tech lists.mpegif.org
>Message-ID:
>
><<mailto:139c4c630801140111l350336b3x9d7920c930e285f6 mail.gmail.com>139c4c630801140111l350336b3x9d7920c930e285f6 mail.gmail.com>
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>
>Hi,
>
>
>I am looking for the predictor of the block that is located at the same
>p[osition in the previous frame.
>
>IN ME-umhex.c , i have found this....
>
>//prediction using mV of last ref moiton vector
> if(pred_MV_ref_flag == 1) //Notes: for interlace case, ref==1 should
>be added
> {
> cand_x = pic_pix_x + (pred_MV_ref[0]/4);
> cand_y = pic_pix_y + (pred_MV_ref[1]/4);
> SEARCH_ONE_PIXEL
> }
>
>
>However in Me-EPZS.c , i am unable to find this one, Probably there it does
>not exists, as all the other temporal predictors are present.
>
>If yes then can anyone point out?
>
>Thanks and Best REgards
>Humaira
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--
David Singer
Apple/QuickTime
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