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| author | Michele Calgaro <michele.calgaro@yahoo.it> | 2020-09-11 14:38:47 +0900 |
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| committer | Michele Calgaro <michele.calgaro@yahoo.it> | 2020-09-11 14:38:47 +0900 |
| commit | 884c8093d63402a1ad0b502244b791e3c6782be3 (patch) | |
| tree | a600d4ab0d431a2bdfe4c15b70df43c14fbd8dd0 /debian/transcode/transcode-1.1.7/docs/import_v4l2.txt | |
| parent | 14e1aa2006796f147f3f4811fb908a6b01e79253 (diff) | |
| download | extra-dependencies-884c8093d63402a1ad0b502244b791e3c6782be3.tar.gz extra-dependencies-884c8093d63402a1ad0b502244b791e3c6782be3.zip | |
Added debian extra dependency packages.
Signed-off-by: Michele Calgaro <michele.calgaro@yahoo.it>
Diffstat (limited to 'debian/transcode/transcode-1.1.7/docs/import_v4l2.txt')
| -rw-r--r-- | debian/transcode/transcode-1.1.7/docs/import_v4l2.txt | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/debian/transcode/transcode-1.1.7/docs/import_v4l2.txt b/debian/transcode/transcode-1.1.7/docs/import_v4l2.txt new file mode 100644 index 00000000..9b7e264a --- /dev/null +++ b/debian/transcode/transcode-1.1.7/docs/import_v4l2.txt @@ -0,0 +1,97 @@ +--- README --- + +What + +This module captures from v4l2-compatible cards. I made it because the +existing v4l import module uses the v4l-compatibility-layer of most +cards nowadays, which is not what you want. Also the v4l module does not +keep track of audio-to-video synchronisation in any way. This may be +sufficient for some capturing cards, but my own SAA7134-based looses a +frame every now and then so audio and video will become unsynchronised +after a while. + +Who + +Anyone using a capturing card compatible to v4l2 should be able to use +the module, there are some warnings applicable though. First, I can only +test on a SAA7134-based card. I do follow general v4l2 programming +directives, so in theory it should work on any v4l2 compatible card. The +SAA7134 driver does have some quirks though. The module detects SAA7134 +based cards and enables some workarounds. I can imagine that other +drivers that also need workarounds, these are of course not present in +the module. Second, the v4l2 api changes frequently. If you'd like to +compile the module yourself, you may run into all sorts of problems, +including compiling errors and errors during runtime of transcode. +Sometimes these problems can be solved by adding another include file to +the source, but you need to have linux kernel version > 2.4.20 anyway +and also with the latest v4l2 patches applied (see +http://www.bytesex.org). Linux version >= 2.6.0 should work in theory, +but I didn't test on it. + +How + +1) Set v4l2 parameters (station, bright, volume, etc.) using your +favourite tv viewing program or something like v4lctl. I deliberately +did not include any setting of parameters in the module as these +external programs are much better at it anyway ;-) + +2) Try!!! You should be able to record from v4l2 now with transcode +using "-x v4l2". You may have to use "-D" to correct any static (!) +difference between audio and video, this depends on your card etc. You +should also use -V, because the SAA7134 driver seems to have a problem +with RGB capturing, which crashed my computer, so I disabled the +capture-in-RGB mode for the moment. Most encoders work much better and +faster with YUV anyway. + +For SAA7134 cards, you may choose to record audio from the card directly +(using direct PCI transfers, not using sound cards etc.) To enable this +mode, add "oss=1" to the saa7134 driver module parameters. You now +should have another dsp device (mostly /dev/dsp1, sometimes /dev/dsp2). +To use this device for capturing, pass it to transcode with the -p +flag. Keep in mind that this device can only capture at 32 Khz, although +it will happily accept any other rate. You may have to use the resample +filter. + +3) If your cpu can hardly keep up it is advisable to boost up the number +of internal transcode buffers to e.g. 128 (-u 128). You may run into +this situation if you're encoding to mpeg2 in real time. If that's not +enough, you cpu is simply too slow for what you want :-( You'll have to +tweak. Sometimes, if you're also using filters, it helps to change the +number of threads. + +4) If your cpu can cope and also the number of v4l2 buffers is +sufficient (full screen capture should report six buffers) and the +transcode buffers are not overrun (watch the number between +parenthesises), and your audio and video become out-of-sync, then you +should try the force resync mode. Else happy capturing! ;-) + +5) You can enable and tune the resync mode using parameters to +the v4l2 module (-x v4l2="<param>:<param>:etc"). + +Possible parameters: + +resync_margin=x this many frames the audio and video may drift + apart before frame dropping or cloning starts. +resync_interval=x this many frames between each resynchronisation + check +overrun_guard=x set this to 1 if you have a saa7134 and a very old + driver (pre-2004) +crop=wxh+txl use hardware cropping width * height at top / left; + only works on recent saa7134 driver +convert=x specifiy conversion scheme manually. + x is a number, obtained with convert=-1, -2 = auto (default) +format=x specify colour format manually, use format=list + to obtain a list. + +Please note: if you do not need the resync mode, do not enable it! If +your card produces good a/v sync ON AVERAGE (although short variations +may exist) the resync code will do more harm than good. Resyncing works +by cloning and dropping frames and yes, this is visible! On the other +hand, a hickup every now and then may be more acceptable than audio +running before or behind. Your milage may vary ;-) If you determined +that you definitely need the resync mode, then you should tune the +resync parameters. A good start is resync_margin=2,resync_interval=15. +Whenever "info output" is "on" (-q 1) and a frame is cloned or dropped, +transcode will show a line with some parameters, like whether the frame +is dropped or cloned and the sequence numbers of audio and video. When +finished encoding, a summary is shown. |
