iTunes internals

[Anonymous]

@rpedde wrote:

-T I think shows the metadata tree. You’re checking if the mdat atom is at the end, not at the beginning.

Creating a file like this:

ffmpeg -i Filename_avi-avi.avi -vcodec mpeg4 -bufsize 65536 -maxrate 1000k -b 716800 -qmin 3 -qmax 5 -g 300 -s 320x240 -aspect 4:3 -acodec libfaac -ar 44100 -ab 128k -async 1 -f mp4 "Filename_mp4-mp4 (SpecOpts).mp4"

will give the following output from AtomicParsley -T

Atom ftyp @ 0 of size: 20, ends @ 20

Atom free @ 20 of size: 8, ends @ 28

Atom mdat @ 28 of size: 373402548, ends @ 373402576

Atom moov @ 373402576 of size: 3381993, ends @ 376784569

Atom mvhd @ 373402584 of size: 108, ends @ 373402692

Atom trak @ 373402692 of size: 1245557, ends @ 374648249

Atom tkhd @ 373402700 of size: 92, ends @ 373402792

Atom mdia @ 373402792 of size: 1245457, ends @ 374648249

Atom mdhd @ 373402800 of size: 32, ends @ 373402832

Atom hdlr @ 373402832 of size: 45, ends @ 373402877

Atom minf @ 373402877 of size: 1245372, ends @ 374648249

Atom vmhd @ 373402885 of size: 20, ends @ 373402905

Atom dinf @ 373402905 of size: 36, ends @ 373402941

Atom dref @ 373402913 of size: 28, ends @ 373402941

Atom stbl @ 373402941 of size: 1245308, ends @ 374648249

Atom stsd @ 373402949 of size: 184, ends @ 373403133

Atom mp4v @ 373402965 of size: 168, ends @ 373403133

Atom esds @ 373403051 of size: 82, ends @ 373403133

Atom stts @ 373403133 of size: 24, ends @ 373403157

Atom stss @ 373403157 of size: 5132, ends @ 373408289

Atom stsc @ 373408289 of size: 28, ends @ 373408317

Atom stsz @ 373408317 of size: 619968, ends @ 374028285

Atom stco @ 374028285 of size: 619964, ends @ 374648249

Atom trak @ 374648249 of size: 2136320, ends @ 376784569

Atom tkhd @ 374648257 of size: 92, ends @ 374648349

Atom mdia @ 374648349 of size: 2136220, ends @ 376784569

Atom mdhd @ 374648357 of size: 32, ends @ 374648389

Atom hdlr @ 374648389 of size: 45, ends @ 374648434

Atom minf @ 374648434 of size: 2136135, ends @ 376784569

Atom smhd @ 374648442 of size: 16, ends @ 374648458

Atom dinf @ 374648458 of size: 36, ends @ 374648494

Atom dref @ 374648466 of size: 28, ends @ 374648494

Atom stbl @ 374648494 of size: 2136075, ends @ 376784569

Atom stsd @ 374648502 of size: 91, ends @ 374648593

Atom mp4a @ 374648518 of size: 75, ends @ 374648593

Atom esds @ 374648554 of size: 39, ends @ 374648593

Atom stts @ 374648593 of size: 24, ends @ 374648617

Atom stsc @ 374648617 of size: 28, ends @ 374648645

Atom stsz @ 374648645 of size: 1067964, ends @ 375716609

Atom stco @ 375716609 of size: 1067960, ends @ 376784569

Total size: 376784569 bytes; 39 atoms total. AtomicParsley version: 0.9.0 (utf8)

Media data: 373402548 bytes; 3382021 bytes all other atoms (0.898% atom overhead).

Total free atom space: 8 bytes; 0.000% waste.

So if I understand you correct about the mdat atom, this file should be streamable… Correct?
It’s playable through the FS any way.
@rpedde wrote:

@turbo wrote:

The changed testing phase is to set mp4v files to be SSC transcoded, make sure the script simply cat’s the file to STDOUT. This works when clicking on the actual file I want streamed.. But if clicking the AVI file (still cat’ing the streamable – working – MPEG4IP converted/fixed file though!) will (still!) make iTunes to hang up.. This is how I’ve been testing this previously, so apparently iTunes notices that it isn’t getting the file requested… ?!?

probably from a different codec type.

different codec type? How do you mean?

I’ve faked the codec type in the DB so that the AVI looks like an MP4 – update songs set codectype=’mp4v’,type=’m4v’ where path like ‘%.avi’ and patch FireFly to send the codectype as Content-Type. Also tried codectype=’mp4a’,type=’m4a’ which would lead to Content-Type: audio/m4a (which is the same Content-Type as streaming the Filename_mp4-mp4 (SpecOpts).mp4 file) to no avail.

But it even though the file is supposed to be streamable (the mdat atom at the beginning and all), it still don’t stream..

Session 0: Transcoding file 'Filename_avi-avi.avi' to 192.168.1.1 (offset 0)

Transcoding /share/Movies/tmp/Filename_avi-avi.avi with ssc-script/0.2.1.1 (codectype=mp4v)

Executing /usr/local/bin/mt-daapd-ssc.pl "/share/Movies/tmp/Filename_avi-avi.avi" 0 600.000 "mp4v"

Updating Content-Type from application/x-dmap-tagged to audio/m4v

Updating Connection from close to Close

Emitting reponse header Expires: -1

Emitting reponse header Cache-Control: no-cache

Emitting reponse header DAAP-Server: firefly/0.2.1.1

Emitting reponse header Accept-Ranges: bytes

Emitting reponse header Content-Language: en_us

Emitting reponse header Content-Type: audio/m4v

Emitting reponse header Server: mt-daapd/0.2.1.1

Emitting reponse header Connection: Close

Emitting reponse header Date: Sat, 22 Dec 2007 14:02:13 GMT

DEBUG: Streaming symlink '/share/Movies/tmp/Filename_mp4-mp4 (SpecOpts).mp4'

DEBUG: Transcoding started (pid=)...

DEBUG: Waiting for stream...

DEBUG: Starting to stream from '/tmp/t-20193'.

DEBUG: 1(4096) 2(4096) 3(4096) 4(4096) 5(4096) 6(4096) 7(4096) 8(4096) 9(4096) 10(4096) 11(4096) 12(4096) 13(4096) 14(4096) 15(4096) 16(4096) 17(4096) 18(4096) 19(4096) 20(4096) 21(4096) 22(4096) 23(4096) 24(4096) 25(4096) 26(4096) 27(4096) 28(4096) 29(4096) 30(4096) 31(4096) 32(4096) Error writing to client socket: Broken pipe

ERROR: Buffer write failed ('' != '4096'): Broken pipe

id          path                                    type        codectype   has_video









2           /share/Movies/tmp/Filename_avi-avi.avi  m4v         mp4v        1

15          /share/Movies/tmp/Filename_mp4-mp4 (Sp  m4a         mp4a        0         

So… As I understand it, it should stream!

Clicking on the id=15 file, iTunes will stream. The sound anyway (because of the type=m4a). So changing the id=2 file to have the same values (including has_video, description etc) as id=15, iTunes should play the sound at least, right?

Well, it doesn’t…

@rpedde wrote:

@turbo wrote:

What’s going on here!?

Nary a clue. But as mentioned before, you aren’t going to get this work with simple shell scripts. You’re going to *have* to have something to synthesize headers, like wavstreamer does only with m4v.

Tripple checking that the Filename_mp4-mp4 (SpecOpts).mp4 is actually streamable through the perlscript, I simply link that file to the temp file the script uses and click the filename in iTunes (I’ve also set mp4a to always transcode). And as expected, it works (sound anyway, but that was expected). I can see the script being invoced and ‘link’ being streamed.

@rpedde wrote:

Also, I’m not sure you are going to be able to stream anything but m4v (or something transcoded to m4v), since most of the quicktime plugins require seekable streams.

Fair enough. QuickTime is a quite sucky format any way. But I didn’t have much more luck with MP4…
@rpedde wrote:

The only think I *know* will stream with quicktime is m4v.

FireFly have now started to crash when it starts to stream the file. Don’t know if this is because the changes to the DB, FireFly or something else… I’ll try to figure out why. With a little luck I can get it to stream MP4’s as soon as I figure out why it’s crashing…

[Anonymous]

@turbo wrote:

FireFly have now started to crash when it starts to stream the file.

My bad (script error).

I stream a file that I know is streamable, in a format that iTunes understands, etc, etc. But still fails….

I’m starting to loose hope here. There must be something I’m missing… I just can’t figure out what 🙂

[rpedde]

@turbo wrote:

So if I understand you correct about the mdat atom, this file should be streamable… Correct?

No. The mdat atom is the one called “mdat” — the third one in, after a small amount of unused space, and a header. That has to be *after* all the other atoms. If it isn’t it won’t stream. It will play on a local fs, but it won’t stream. Not from iTunes, not from mt-daapd. Not from anything.

Specifically, things like sample rate and that sort of thing come from moov:trak:mdia:minf:stbl:stsd:mp4a (and mp4v). If it can’t pull sample rates and codectypes from that *before* it sees the mdat, then it can’t stream it.

different codec type? How do you mean?

I’ve faked the codec type in the DB so that the AVI looks like an MP4 – update songs set codectype=’mp4v’,type=’m4v’ where path like ‘%.avi’ and patch FireFly to send the codectype as Content-Type. Also tried codectype=’mp4a’,type=’m4a’ which would lead to Content-Type: audio/m4a (which is the same Content-Type as streaming the Filename_mp4-mp4 (SpecOpts).mp4 file) to no avail.

That’s exactly what I mean. If you tell iTunes it’s a mp4 file and then give it an avi file to decode, it will barf. No less than if you try and play a flac file with an mp3 decoder. It won’t work.

[Author]

Posts