OK, last quest here, than I can write my mac hdtv transcoding guide.
All attempts to successfully re-encode an m2v file at a lower bitrate have failed. For some reason, everytime I start an encode, the process gets to 100% and finishes, but only ends up encoding anywhere between 1:10 to 1:25 of the 1:30 minute film. It never finishes the whole thing. I thought it might be problems with the m2v stream, but I have checked and it is fine.
This is tough to isolate because it takes 8-10 hours to re-encode, only to have it skip the last 15 or so minutes. To get around this possibly, would it work to split the m2v up in chunks and then put them back together with the mpg join tool? Would this mess up the vbr encoding process, or the sync?
Results 1 to 9 of 9
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Yup, m2v only, muxing in synced ac3 later.
Using ffmpeg mpeg2 engine. Original file 12GB, 1920x1088 29.97 fps interlaced. Going to 1904x800 final res (cropping), 23.976 film (w de-interlace). 8000 kbps bitrate, no audio. High quality, b-frames, two-pass and trellis options. No profile, 12 keyframes, qmin 1, qmax 31.
Everything is perfect. Image quality is stunning, crops perfectly, de-interlaces perfectly, just stops short of the full movie.
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i've done some more testing and it seems to be a hit or miss thing. it just ends before it's really done encoding. I tested a 30 min file three times, and the second time I got
"video:1498212kB audio:0kB global headers:0kB muxing overhead 1.225341%
bench: utime=8302.470s
Encoding completed on Wed Dec 1 06:48:06 EST 2004"
at the end of the log, and both the first and third time the last line of the log was
"[mpeg2video @ 0x35e2b8]MPEG motion vector out of boundary"
with no encoding complete.
possibly something with the two pass encoding erring out? it gets through the first pass perfectly.
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I think it's some sort of Voodoo.
I've had the ffmpeg engine quit prematurely for no apparent reason also. Mostly when converting AVIs.
One thing I try with problem MPEGs is to open them in MPEG Streamclip and convert them to a transport stream. Then I open the .ts and convert it back to either MPEG or M2V. Sometimes it works. You'll have to mux the M2V to a MPEG to open it in streamclip though. You might try the 'Fix Timecode Breaks' also.
Good Luck.
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yah, these originally came from transport streams, so I did fix the time code breaks, then demux to m2v and ac3, before I ran through ffmpeg
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VooDoo.
I looked back, and the last time I had it quit prematurely was on a Video only encode. Coincidence? I can't remember any further back, but I still have that particular file on my HD. It was a MOV file with MPEG-4 audio. I had deleted the sound track due to the MPEG-4 audio bug. It quit 18 minutes from the end of a 2 hour 36 minute 3ivx video only movie. Maybe try muxing the tracks then encoding?
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Actually, I may have figured it out! Trivial really. I watched ffmpeg work through the 10 hour of encoding time at work today, and on the first pass, it goes through the whole movie, and the size of the file is correct. I can open the mpg in quicktime or VLC and it will show a run time of 2:03:16. Despite some encoding errors due to the first pass, it is all there.
But on the second pass, it will only encode a maximum of 4096MB. Wherever this lies in the movie is where it will stop encoding and finish. For my movie this just happened to be at 1:22:57.
I assume the way a 2 pass encode works, is by replacing the original file's frames with the optimized frames from the second render. Opening the finished product in quicktime will show a data size of 4096MB, although the actual file size in the finder is over 7GB. THis is because, the second pass didn't rewrite all the frames, so the original encoded data is still there, beyond the 4096 limit, but is not viewable due to the end of file marker after the 4096th MB.
Soooo, my conclusion is that the 2nd encoding pass via ffmpeg's MPEG2 encoding engine is hitting the fat16 or hfs file limit of 4GB and stopping regardless of what is left. This happens when processing high defenition video in a greater than 8gb file size. phew.
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nope. ha ha I was wrong. after talking with some folks at apple, they told me this is a "feature" of quicktime. the 4096mb limit will be upgraded in quicktime 7 for os 10.4 released next year, but until then, you are stuck with that hfs limit now. still haven't figured out the encoding problem. finally got a complete render of the full movie. trying all options as well. now on to syncing ac3 for the moment.
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