Audio sync issue after making DVD ISO

unmun wrote on 1/6/2020, 3:51 PM

I've been trying to get this sorted for a few days now, haven't been able to find any solution so I thought I'd post here. I'll try and include as much info about my workflow & software as I can - hopefully someone can help!

I'm making a DVD of an event - it's a series of interviews. I edit each interview with Blender and generate an MPEG for each one.

Then I use ffmpeg to concatenate all the MPEGs into a DVD compliant one using the -target pal-dvd option.

Then I use DVD Architect 7 (build 100) to make a DVD ISO.

When I watch the DVD MPEG with VLC, the audio is in sync throughout the entire video - about 1h 50m.

When I watch the ISO with either VLC or on a real DVD player, the audio drifts out of sync. It is about 1/3 second out of sync by the end of the video.

Here's the MediaInfo of one of the Blender-generated interview parts:

General
Complete name                            : C:\Users\Dave\Videos\not-a-number\p1.mpeg
Format                                   : MPEG-PS
File size                                : 2.24 GiB
Duration                                 : 26 min 20 s
Overall bit rate mode                    : Variable
Overall bit rate                         : 12.2 Mb/s

Video
ID                                       : 224 (0xE0)
Format                                   : MPEG Video
Format version                           : Version 2
Format profile                           : Main@High
Format settings, BVOP                    : No
Format settings, Matrix                  : Default
Format settings, GOP                     : Variable
Duration                                 : 26 min 20 s
Bit rate mode                            : Variable
Bit rate                                 : 11.5 Mb/s
Maximum bit rate                         : 12.0 Mb/s
Width                                    : 1 920 pixels
Height                                   : 1 080 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 FPS
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.222
Time code of first frame                 : 00:00:00:00
Time code source                         : Group of pictures header
GOP, Open/Closed                         : Open
GOP, Open/Closed of first frame          : Closed
Stream size                              : 2.12 GiB (95%)

Audio
ID                                       : 189 (0xBD)-128 (0x80)
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Muxing mode                              : DVD-Video
Duration                                 : 26 min 20 s
Bit rate mode                            : Constant
Bit rate                                 : 384 kb/s
Channel(s)                               : 6 channels
Channel layout                           : L R C LFE Ls Rs
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Delay relative to video                  : 27 ms
Stream size                              : 72.4 MiB (3%)
Service kind                             : Complete Main

Here's the MediaInfo from the ffmpeg-generated DVD-compliant MPEG:

General
Complete name                            : C:\Users\Dave\Videos\not-a-number\not-a-number-pal-dvd.mpeg
Format                                   : MPEG-PS
File size                                : 4.84 GiB
Duration                                 : 1 h 49 min
Overall bit rate mode                    : Variable
Overall bit rate                         : 6 322 kb/s

Video
ID                                       : 224 (0xE0)
Format                                   : MPEG Video
Format version                           : Version 2
Format profile                           : Main@Main
Format settings, BVOP                    : No
Format settings, Matrix                  : Default
Format settings, GOP                     : Variable
Duration                                 : 1 h 49 min
Bit rate mode                            : Variable
Bit rate                                 : 5 748 kb/s
Maximum bit rate                         : 9 000 kb/s
Width                                    : 720 pixels
Height                                   : 576 pixels
Display aspect ratio                     : 16:9
Frame rate                               : 25.000 FPS
Standard                                 : PAL
Color space                              : YUV
Chroma subsampling                       : 4:2:0
Bit depth                                : 8 bits
Scan type                                : Progressive
Compression mode                         : Lossy
Bits/(Pixel*Frame)                       : 0.554
Time code of first frame                 : 00:00:00:00
Time code source                         : Group of pictures header
GOP, Open/Closed                         : Open
GOP, Open/Closed of first frame          : Closed
Stream size                              : 4.40 GiB (91%)

Audio
ID                                       : 189 (0xBD)-128 (0x80)
Format                                   : AC-3
Format/Info                              : Audio Coding 3
Commercial name                          : Dolby Digital
Muxing mode                              : DVD-Video
Duration                                 : 1 h 49 min
Bit rate mode                            : Constant
Bit rate                                 : 448 kb/s
Channel(s)                               : 6 channels
Channel layout                           : L R C LFE Ls Rs
Sampling rate                            : 48.0 kHz
Frame rate                               : 31.250 FPS (1536 SPF)
Compression mode                         : Lossy
Delay relative to video                  : -5 ms
Stream size                              : 351 MiB (7%)
Service kind                             : Complete Main

In both cases the audio frame rate is 31.250. It seems that might be causing the issue with DVDA? I don't know how I can change that - until now I wasn't aware that some audio formats have a frame rate.

This also happens if I just concatenate all my parts together and have DVDA convert it for DVD. I assume because the audio frame rate is still wrong.

Any help would be much appreciated! It's frustrating that it plays fine in VLC, but just when rendered onto a DVD it goes wrong.

Can DVDA be configured to ignore the audio frame rate?

Thanks!

Comments

EricLNZ wrote on 1/6/2020, 8:15 PM

I don't know the answer but have a suggestion. Try telling DVDA to recompress the audio, even though you will recompress it to AC3.

Dot wrote on 1/6/2020, 10:37 PM

One thing I notice is that you said you were only concantenating the files in FFMPEG but the bitrate for your audio got changed. That could be causing an issue.

unmun wrote on 1/12/2020, 11:46 AM

I think what was happening was that each audio codec has a delay relative to the video, and when I concat that delay adds up for each video.

I guess VLC doesn't care about that, or is a bit loose with it whereas maybe DVDA pays more attention to it. Hence why VLC played it ok, but DVDA didn't.

I tried like 12 combinations of ffmpeg and DVDA settings and eventually resolved it by using -af aresample=async=1000 with ffmpeg which stretches the audio to make sure the timestamps line up with the video.

I've made DVDs previously with the same workflow and didn't run into this issue, so I'm at a loss as to why this happened this time.

Thanks for the two responses. I thought I'd post my solution here in case it helps someone else with a similar problem.