July 2007 - ffmpeg-devel - lists.ffmpeg.org

[FWD] [PATCH] immediate decoding of dvd stills
by nicola_sabbi＠fastwebnet.it 23 Jun '11

23 Jun '11

Some time ago someone posted this small patch to permit decoding dvd still images without setting LOW_DELAY; unfortunately it seems the patch was forgotten Is it ok to commit? If not, what's the right way to proceed?

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[PATCH] DCA-in-WAV detection
by kostya.shishkov＠gmail.com 26 Jan '11

26 Jan '11

Here is my attempt on patch discussed on Febryary 2006 Thread called "[PATCH] Fix DTS in WAV file playback."

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[PATCH] Apple Video Encoder (rpza)
by ffmpeg.php＠gmail.com 23 Jan '11

23 Jan '11

Attached is a patch to add support for Apple Video encoding (rpza). The quality settings are defined at compile time right now since I wasn't really sure how to map ffmpeg's numerous video options to the capabilities of rpza. It supports all rpza encoding opcodes but the 4-color block encoding doesn't try to do multiblock runs yet. -Todd

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[PATCH]wmv3 encoder
by fortin＠nerim.net 23 Jan '11

23 Jan '11

Hi, The following patch adds a wmv3 encoder (i removed the vc1 encoder because it doesn't generate an elementary stream). I don't think i can split the patch without breaking compilation between two patches. Please comment (particularly the vc1enc.h include in mpegvideo.c). Thanks, Denis

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[PATCH] Chinese AVS encoder
by stefan.gehrer＠gmx.de 23 Jan '11

23 Jan '11

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Hi, as announced before here is my encoder for Chinese AVS. Features that it does support: - - Intra macroblocks - - P_SKIP macroblocks - - P_16x16 macroblocks - - one or two reference frames - - constant quantizer encoding - - motion estimation using hexagon search and qpel refinement Features that it does not support: - - P_16x8, P_8x16 and P_8x8 macroblocks - - B macroblocks/frames - - rate control - - anything else you might think of To test it, here is a sample command line ./ffmpeg -i in.avi -vcodec cavs -strict -2 -cqp 30 -refs 2 -psnr out.avi - -strict -2 is required for the encoder's experimental nature, I have not thought much about its standard conformance, just that it decodes with my decoder. - -cqp n with n in the range 0 to 63 is required as only fixed quantizer encoding is supported - -refs 2 is optional, one reference frame would be the default - -psnr is optional Michael, regarding your question on cvslog (sorry for crossposting, I wasn't subscribed to cvslog at the time): >> Author: stefang >> Date: Sat Jul 7 09:14:58 2007 >> New Revision: 9518 >> >> Log: >> move dequantization into it's own inline function > >why inline? same question for the other inline functions >is there some speed gain from duplicating them in the object files >between encoder and decoder? To be honest I did not think much about object size, it just seemed to be a convenient way to share functions this way instead of having to create ff_cavs_foobar names and without creating function call overhead that was not there before. If you think object size would be a problem I can of course move some functions back from cavs.h to cavs.c. Stefan -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFGocyhYpYOlpT3vNMRArJrAKC5aQQ40GEmegoLh8u0b0HCc0f60QCgzgc4 tMea5NiHbnlzxikJYvkl9Q4= =0R8q -----END PGP SIGNATURE-----

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[PATCH] GSM-MS decoder and encoder
by mbardiaux＠mediaxim.be 01 Feb '10

01 Feb '10

-- Michel Bardiaux R&D Director T +32 [0] 2 790 29 41 F +32 [0] 2 790 29 02 E mailto:mbardiaux at mediaxim.be Mediaxim NV/SA Vorstlaan 191 Boulevard du Souverain Brussel 1160 Bruxelles http://www.mediaxim.com/

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compressed v4l2 images
by ramiro＠lisha.ufsc.br 10 Dec '09

10 Dec '09

Hello, I have a webcam running the zc0301 driver. On the VIDIOC_S_FMT ioctl call, it always sets the pixel format to V4L2_PIX_FMT_JPEG. The current code doesn't take into account when the pixel format is changed on that call. Also, it doesn't support the compressed JPEG stream even if the pixel format is changed according to the result of the ioctl. What's the best way to make it support compressed JPEG? Just check for compressed and set appropriate codec_id? Ramiro Polla

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Understanding motion vectors from ff_print_debug_info()
by pro＠cs.washington.edu 12 Aug '09

12 Aug '09

Hey All- A while back Paolo suggested that people looking to extract motion vectors in ffmpeg should look at the method ff_print_debug_info() in libavcodec/mpegvideo.c. This advice turned out to be very useful in my case. Thx Paolo. However, I have a couple of questions about the constants being used ff_print_debug_info() that would really help noobs like myself really understand what is going on. Please consider posting a reply if you are familiar with this part of ffmpeg. # It looks like you have to divide by 2 (or a higher power of 2) the values in the motion_val array to obtain the true motion vectors. Why is this so? For example ff_print_debug_info() processes the motion_val vectors in the following manner: motion_val[direction][xy][0]>>shift where shift = 1 + s->quarter_sample. The 'quarter_sample' variable makes sense. It's accounting for some sort of mode where the video is sub-sampled by 2 in the X and Y axis. But I don't understand why the '1' is added to 'shift' in effect dividing all motion vectors by 2. # For computing the 'mv_stride' variable avcodec.h suggests the following formula: mv_stride= (mb_width << mv_sample_log2) + 1 While I don't understand why that '1' is added mv_stride. What worries me is that the addition of that '1' is conditional and I don't understand when not to add that '1'. For example ff_print_debug_info() uses the following formula: (s->mb_width << mv_sample_log2) + (s->codec_id == CODEC_ID_H264 ? 0 : 1) # Finally, is there any way to populate the AVFrame.motion_val array with the motion vectors without having the motion vectors visualized on the decoded video frame? I'm setting AVCodecContext.debug_mv = 1 to obtain the motion vectors but as a side effect that flag also draws the motion vectors. It looks like ff_print_debug_info() always draws the motion vectors when the debug_mv flag is set. It seems wasteful to have to decode the video twice in order to obtain the motion vectors and the video frames without the visualization. Thank you for your time. -pro

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[PATCH] DV timecode
by baptiste.coudurier＠smartjog.com 02 Feb '09

02 Feb '09

Hi 3 patches: - add timecode.h to avoid code duplication for drop frame timecode adjustment - use new lavc timecode api to set timecode in DV. Regression tests change because now default behaviour is non drop frame timecode, you can still activate it by using -flags2 +drop_frame_timecode - timecode helper function for ffmpeg to set timecode. Maybe moving brktimegm to lavu and using it is better ? -- Baptiste COUDURIER GnuPG Key Id: 0x5C1ABAAA SMARTJOG S.A. http://www.smartjog.com Key fingerprint 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA Phone: +33 1 49966312

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[RFC] ratecontrol buffer size magic
by baptiste.coudurier＠smartjog.com 29 Nov '08

29 Nov '08

Hi, I stumbed accross a weird behaviour of the CBR ratecontrol lately, basically doing: ffmpeg -i file.mpg -vcodec mpeg2video -minrate 30000k -maxrate 30000k -b 30000k -intra -flags +ildct+low_delay -dc 10 -flags2 +ivlc+non_linear_q -ps 1 -qmin 1 -qmax 12 -top 1 -vglobal 4 -acodec pcm_s16be -f mov -bufsize 1200000 -rc_init_occupancy 1200000 cbr.mov Constraints are so in order to achieve vbv delay as 3600. Now ffmpeg will only give me qp as 24. While tweaking I changed some magic in ratecontrol.c (see patch attached) and now qp have decent/good values. I dig into svn history and found out that r2601 bumped */2 to */3 to improve CBR ratecontrol. Can anyone explain in detail why that magic does improve behaviour ? Can that parameter be user setable ? Or is it really hardcoded everywhere ? Am I doing something terribly wrong ? Thanks for comments. -- Baptiste COUDURIER GnuPG Key Id: 0x5C1ABAAA SMARTJOG S.A. http://www.smartjog.com Key fingerprint 8D77134D20CC9220201FC5DB0AC9325C5C1ABAAA Phone: +33 1 49966312

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