Problems Encoding 720P Material

[stshipley]

Hello all,

I am using EyeTV 500 to record HDTV material. ABC and Fox show their material in 720P.

FFmpegX shows 720P material as:
Mpeg 2 Program Stream File [Video/Audio]
Muxrate : 262.18 Mbps

Not interlaced, chroma format:4:2:0
Size 1280x720 59.94 fps 38.81 Mbps

When I try encoding this to Xvid/H.264/Mpeg4, I select 29.97 fps as my frame rate. But the resulting file is slightly jittery. And when I watch the encoding process in the Terminal window, it skips a bunch of frames, as you'd expect, but far less that 29.97 a second. It's more like 20 frames a second. Witness this from the terminal window:

Skipping frame!
Pos: 119.0s 7131f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1785:0]
Skipping frame!
Pos: 119.0s 7133f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1785:0]
Skipping frame!
Pos: 119.1s 7137f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.1s 7139f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.2s 7143f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.2s 7145f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.3s 7149f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.3s 7151f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.4s 7155f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]
Skipping frame!
Pos: 119.4s 7157f (97%) 7fps Trem: 0min 26mb A-V:0.000 [1786:0]

If you watch the skipped frames, it's not every other frame, it's 2 out of every 6 frames. The pattern is consistant.

As a result, you can see some jitter in the playback.

I have no idea if this is a by product of that, but as time goes on, the audio outpaces the video and become seriously out of sync.

Any ideas on a solution?

BTW, I don't have this problem with 1080i HD material.

Thanks in advance,

-STS

[stshipley]

Hmm no repsonse . . . .

I am currently able to get around this issue two ways -

1) Use ffmpegx XVID/MPEG4. It is the Mencoder that is unable to correclty drop every other frame.

2) Convert the file from Mpeg2 to MPEG_TS. The MPEG_TS is ffmpegx rather than mencoder, so I am able to use it to drop half the frames and get from 59.94 fps to 29.97 fps. THEN, I can encode it the H.264 or any other mencoder codec.

-STS

[major]

Can you send me a link to download a small clip of your file?

[stshipley]

Major, what size file would you like as a test? One minute is on the order of 100MB.

-STS

[major]

A clip just big enough to notice the sync problem.

[stshipley]

Major,

I hope you got my various emails that direct you download the files you requested. If you did not, or cannot retrieve them, please email me at scott-shipley@comcast.net

These files aren't long enough to show the sync issue, which only manifestes itself over time, but in encoding it, you can see the failure of mencoder to delete every other frame, and thus a slightly jittery resultant file is created.

Thanks,

-STS

[major]

OK, I'm downloading them now.