December 2007 - ffmpeg-devel - lists.ffmpeg.org

[FWD] [PATCH] immediate decoding of dvd stills
by nicola_sabbi＠fastwebnet.it 24 Jun '11

24 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 24 Jan '11

24 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] Implement PAFF in H.264
by heydowns＠borg.com 26 Mar '10

26 Mar '10

Attached is a patch that implements PAFF in H.264. I don't expect this to be accepted right away, due to size and complexity, but I want to get it out there for review and for people to try out and comment on. It is working stable for me on a number of samples, including ones that mix PAFF with progressive and/or MBAFF. Basic overview of how it works: 1. Fields are decoded and deinterlaced. 2. If non-paired fields are encountered, they are not output, but are used for reference if so marked. 3. Reference lists are kept as they were before, but now may also contain unmatched field pairs. Reference list construction splits field pairs out to fields as needed. There is a major shortcoming/known issue with this patch; it disables the error concealing calls for field pictures. This is because the error concealer needs slices to be contiguous regions of the picture buffers. I'd appreciate input on how best to augment the error concealer to handle interlaced slices (or if I am just missing something....) Also interested in hearing how this should be split into smaller patches (I know that at least the addition/changes to header documentation should come out). -Jeff

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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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h264 multithreading, chapter 2
by andreas＠olebyn.nu 01 Apr '09

01 Apr '09

Hi, Even though I previously dismissed speeding up h264 decoding by splitting entropy decoding from the rest in two threads I decided to take a quick shot at it. The attach patch gives ~20-30% speedup on single sliced CABAC content. Basically, the code decodes up to 128 macroblocks in one thread while doing prediction+idct+deblock of the previously decoded 128 blocks in another thread. 20-30% is not exceptionally much, I would have expected a bit more. If you have a look in the patch you'll notice that it brutally copies the relevant fields back and forth from the H264Context. I tried embedding the H264mb into H264Context so i could reduce it into one single memcpy(), this does not make any difference (expect that it makes the patch about 3000 lines longer :-) I also tried passing an additional pointer around to all functions to entirely get rid of the memcpy()ing. This does not make any significant change either (And I know from my first attempts with slice-level multi threading that this slows down the single threaded case). All this kind of makes sense (i think) if you ponder that the data needs to be transfered from CPU1's cache to CPU2's cache (if it's even still around in CPU1's cache). Even with some type of shared cache mechanism (I'm not actually sure how core2 duo does this) the probability that the data from the previous 128 macroblocks still is in place is probably minimal. I tried lowering the number of macroblocks processed per round, but the overhead of thread synchronization quickly defeats any gain (If you only do one macroblock per round, it's about 7-8 times as slow :-) well well... It is (obviously) not intended/ready for any formal review. MBAFF support is lacking, there is some code-duplication and other ugliness. But rather before I spend any more time on it I'd like to know if people think it is worth finishing. If we in the future also add frame based parallelism we would end up with three different techniques, (== bloated == hard to maintain), then again, perhaps one of them can be removed when we've got the full picture. I dunno... Ideas, hints, test-results, flames are welcome..

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