4GB limit, chunk download, what to use to demux and remux?

[MS]

On 03/08/12 13:52, dinkypumpkin wrote:
> MS wrote:
>> So how do I fix the downloaded chunks? What Linux software do I use to
>> demux my 1st chunk .mp4 file and subsequent chunks .mp4.flv files? And
>> what software do I use to remux them together preferably allowing a
>> little editing to get rid of the 5 min overlaps I've used for the
>> chunks, and fixing the timecode? (If timecode the right expression for
>> the time displayed when playing the video?)
>
> I just use ffmpeg with -ss and -t to trim and re-mux the .flv files.
> I've found that trimming 5 mins from the beginning of each chunk created
> with --start is way more than enough to remove the wonky timestamps.
> I've used Avidemux to concatenate the trimmed and re-muxed chunks.
> mencoder worked as well, though I had to re-encode the audio. I tried
> concatenating with ffmpeg and mp4box, but I couldn't get the right
> incantations.  The splices are a bit rough, but I'm not too bothered
> about that for the competition sessions.  I made a proper edit of the
> opening ceremony, but I used a Mac - I can't say what your best Linux
> option would be.
>
> Just to confirm: the 4GB issue is not a filesystem limitation per se.
> Even if your filesystem can support >4GB files, the stream still ends at
> 4GB. I did a little debugging with rtmpdump, and for whatever reason the
> server appears to turn off the tap at 4GB. It's not worth the time to
> debug further. It will only be a problem again in another 64 years when
> the Olympics return. By then we'll all be streaming directly to our
> brains via McDonald's branded Olympics skull implants, right?

Many thanks for the help dinkypumpkin, I really appreciate it.

I have followed your advice and have used ffmpeg with -ss and -t to trim 
and re-mux the video. It took me quite some time to work through my 
somewhat messy 7 chunks of downloads, 14 GB worth, and calculate the 
start times and duration of the periods of fencing, as I was also 
editing out several 15-20 minute breaks between the action, and so to 
turn my 9 hours of footage into 6.5 hours of the actual fencing and 
medals ceremony.

The ffmpeg process resulted in 10 .mp4 files which I then concatenated 
together by loading the first into Avidemux and then using append to 
append the next 9 .mp4 files. I must admit I was not too confident that 
Avidemux would handle 10 video files totalling 9.5 GB concatenated 
together and spit out a single nice big perfectly formed .mp4 file, but 
it handled it with apparent ease and did it quickly too (less than 5 mins).

Yes I understand that the 4 GB was not a filesystem limit, EXT4 having a 
16 TB filesize limit, but a 32 bit addressing limitation.

When the Olympics return in 64 years (love your use of a nice multiple 
of 2), if I am still alive, which is extremely doubtful as I would have 
received my telegram from a very elderly King William V (or his 
successor), I suspect video formatting issues will be the least of my 
worries. Hopefully Banksian 'mindstate' technology will be up'n'running 
and I'll be principally concerned with software choices concerning the 
upload of my 100 billion neurons and 100 trillion synapses into a 21 
year old (brain empty and waiting to be filled) clone of my body, nicely 
blemish free and at the peak of physical fitness. I am almost 100% sure 
that these software choices will not involve the use of the Unix/Linux 
command line, much as I love it. :)

All the best,

Matt

P.S. Long live Thunderbird, my email slash newsgroup companion since 
early beta releases.