[mythtv-users] Dumping MPEG files to DVDs

[John Pilkington]

On 11/05/16 09:58, Andre Newman MythTV wrote:
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>> On 10 May 2016, at 21:28, John Pilkington <J.Pilk at tesco.net> wrote:
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>> But it's worth pointing out that MythArchive doesn't just dump the recorded file onto the dvd - it uses dvdauthor, and 1.2MB of mythburn.log gives immense detail of the adjustments made by mpeg2enc
>> during the process.  I would expect these to ensure dvd-spec compliance.
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> I don’t believe you can get to dvd compliance from a modern mpeg2 transmission without re-encoding. While there are many tweaks that can be done to improve things, it’s mostly about removing or papering over any dropouts in the stream. There is a different much simpler transport stream wrapper required for dvd than is needed for transmission but this doesn’t change the underlying mpeg2 video encoding. In the UK we have some transmission frame sizes that are not in the dvd spec either but most players will still play them.
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> For example the maximum gop for dvd is very short by modern encoder standards, that cannot ever be changed in a video stream without re-encoding. It was done to keep memory requirements low for dvd players but almost all players now have far more memory and more capable decoders than the spec requires. I’ve also noticed that bluray and hddvd players are a lot more tolerant of out of spec dvds.
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>> ... but perhaps I should get another player before they go extinct.
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> If you’ve found one that plays everything you have then yes get another quick before they change the design. :-)
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> Andre

Thanks for this.  For now I'll check my existing player's operation more 
often.  It still looks to me as if on some disks its reader is failing 
to correct errors in extracting the data stream, so that the 
'verification' by the PC's dvd drive isn't reliable.  I take your point 
about the need for re-encoding, but the burn log suggests that this may 
be being done, selectively; here's a short sample:

    INFO: [mpeg2enc] Enc1    687   687(12) P q=9.24     [0% Intra]
    INFO: [mpeg2enc] Enc1    688   688(13) P q=9.11     [0% Intra]
    INFO: [mpeg2enc] Enc1    689   689(14) P q=9.27     [0% Intra]
    INFO: [mpeg2enc] NEW GOP INIT length 15
    INFO: [mpeg2enc] Enc1    690   690( 0) I q=9.11     [100% Intra]
    INFO: [mpeg2enc] Enc1    691   691( 1) P q=10.67     [0% Intra]
    INFO: [mpeg2enc] Enc1    692   692( 2) P q=10.65     [0% Intra]
    INFO: [mpeg2enc] Mean strm Xhi = 1619278 mean gop Xhi = 1938226 
pXhibr=0.0000 cbr/abr=0/0 under=0
    INFO: [mpeg2enc] SKIP: 675 - reencode actual 710992 (9.0) target 
660286 Q=9.6 BV  = 0.00 cbr=5000000
    INFO: [mpeg2enc] Pass2   675   675( 0) I q=9.00 RETAINED
    INFO: [mpeg2enc] RENC: 676 - reencode actual 233216 (9.8) target 
213379 Q=10.5 BV  = -0.27 cbr=4546349
    INFO: [mpeg2enc] Pass2   676   676( 1) P q=10.53 RECODED
    INFO: [mpeg2enc] SKIP: 677 - reencode actual 147608 (10.3) target 
142733 Q=10.6 BV  = -0.26 cbr=4560859
    INFO: [mpeg2enc] Pass2   677   677( 2) P q=10.62 RECODED
    INFO: [mpeg2enc] SKIP: 678 - reencode actual 175256 (9.9) target 
164775 Q=10.1 BV  = -0.23 cbr=4608061
    INFO: [mpeg2enc] Pass2   678   678( 3) P q=10.14 RECODED
    INFO: [mpeg2enc] RENC: 679 - reencode actual 157040 (9.6) target 
143774 Q=10.1 BV  = -0.22 cbr=4634503
    INFO: [mpeg2enc] Pass2   679   679( 4) P q=10.07 RECODED

Cheers,

John