Re: [Libav-user] Best way to create a fractional ms timer?
On 1 April 2013 10:45, Mike Versteeg wrote: > Thanks John. As I said this is more prone to jitter than a timer event. > I've also remember to change the priority but oddly enough, at least on W7, > it makes no difference: I still get the occasional (exact) 10 ms delay, > which almost never happens when using a timer. > I presume MS Windows still doesn't provide timers with <1ms resolution, be it event-based or something like usleep/nanosleep? I haven't seen your original post, but I've already struggled myself to get reliable 1kHz realtime behaviour without external hardware. I ended up with a busy-wait loop, (hogging the CPU was acceptable in my case). R ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] Source code debugging libav using Xcode
In xcode 3, I simply add a new external build target to which I add the ffmpeg source tree. Add that target as a dependency to your own target, and you should be set. If you want to be extra sure, build ffmpeg with the same compiler you use in your project. BTW, I have a git project up over on github.com/RJVB that shows how to make a monolithic framework out of the FFmpeg libs . ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] QTKit -> Libav: has it ever been done?
On 27 March 2013 10:26, Carl Eugen Hoyos wrote: > No, I am not saying that. > (I don't know.) Heh, I'd be surprised if it does exist. If indeed very few FFmpeg devs have OS X hardware, what would be the reason of existence for such a decoder? :) > It is of course possible that QTKit uses a completely > different format, but one way to find out is to test > your resampling wrapper code with a decoder for which > you know the actual format. Yes. And in parallel, one could dump the captured output, not in some container format as I suggested before, but the raw QTSampleBuffers. It shouldn't be too hard to extract the necessary API (structure definition(s), stub functions, etc) so that one can have platform-independent code for locating the data of interest in those imported QTSampleBuffers and feed it into libav. Provided of course that the encoding part of Brad's code doesn't make use of OS X specific programming language features like ARC. (Which is keeping me from playing with his code because it won't build on my older OS version ...) > Note that an endianess issue is very unlikely because FFmpeg > only supports native endian audio formats (as opposed to So if the QTSampleBuffers contain non-native endian data the FFmpeg-encoded output will inevitably be the "wrong way around" unless it is converted before being encoded. Not? > codecs), a signed / unsigned problem is of course possible > but this should be relatively easy to verify. There must be something relatively simple that underlies Brad's problem. After all, video encoding works fine, so his general approach cannot be completely wrong ... ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] QTKit -> Libav: has it ever been done?
On 27 March 2013 09:58, Carl Eugen Hoyos wrote:
> not use QTKit? There is definitely a native decoder
> that outputs the format that (you believe) QTKit
> offers, and that code would not be OSX specific in
> the end.
Are you saying there's a decoder that outputs the decoded content in
QTSampleBuffer format, tested to be accepted as input by QTKit?
Even if that's the case (and I'm not doubting your word on it), that
still doesn't guarantee that those buffers are filled with the same
kind of data. I recall that Brad's problem is with audio, and the
symptoms suggest that there is some kind of misinterpretation of the
soundbytes. It could be as simple as a disagreement on endianness, or
signed vs. unsigned. His words ('ear piercing screams') also evoke
what happens when you put a mic too close to the speaker it feeds
into, but I fail to see how one would achieve that kind of ringing by
accident in software :)
Would it also be an idea to dump the captured content to a supported
container file, ideally without any additional processing of course,
use that as the input, and try to analyse things from there?
R.
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Re: [Libav-user] Converting audio sample buffer format
Carl Eugen Hoyos wrote: >Brad O'Hearne writes: > >> On Feb 18, 2013, at 3:50 PM, Carl Eugen Hoyos wrote: >> >> > While I have _no_ idea what the "flv audio codec" could >> > be, please use either the aconvert filter or libswresample >> > directly to convert from one audio format to another. >> >> This has turned out to be much more difficult than expected. > >Before you start debugging (the cast to sourceData looks >suspicious): Did you look at doc/examples/filtering_audio.c >and doc/examples/resampling_audio.c ? >I suspect using the aconvert filter has the advantage that >you can do other changes to the audio without additional >code (and bugs). > >In any case, using gdb should quickly show you were the >problem lies. > >Carl Eugen > >___ >Libav-user mailing list >Libav-user@ffmpeg.org >http://ffmpeg.org/mailman/listinfo/libav-user Exactly, but you'd need to build the libav libs yourself, with debugging info. There's another thing that's nagging me. IIUC, the goal here is to convert a buffer of (C) floats into signed shorts. I have some difficulty believing that doing this through a generic workhouse function can be more efficient than writing a simple loop and let a good optimising compiler create the best assembly out of it ... R. ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] How to Convert AV_PIX_FMT_RGB24 to AV_PIX_FMT_YUV420P
Chris Share wrote: >Thanks for the sample code. > >I have a couple of further questions: > >1. If the input data is in a vector of unsigned chars (RGBRGB...), what >is the best pixel format to use? I think that'd by FMT_RGB24 . R ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] ff_log2_tab defined multiple times in the fmpeg 1.1 libraries, bug or feature ??
>Everything prefixed with ff are private symbols in ffmpeg, and as such >are not supposed to be exposed in link libraries, because they are not >part of the public API/ABI. >There are already too many exceptions to this, and this avoided even >more. This pleads for static local copies. BTW, would there be much overhead in declaring ff_log2_tab locally in each function that uses it, with current day compilers? R ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] How can i suspend ffmpeg's file reading?
Hello Jack How do you launch ffmpeg and on what os? If you have a process id for it, you could sigstop/suspend it while you wait for data, but that too would of course halt the playing. I've never tried, but I suspect that it would however resume playing when you sigcont/release the process. Alternatively, buffer your stream, measuring download speed and expected bitrate during playback, so that you can launch ffmpeg only when you have downloaded enough content to be reasonably sure that you won't catch up with the download head. This is more or less how QuickTime handles streaming playback, but it isn't failure proof against net congestion or other unforeseen events. René Quy Pham Sy wrote: >Hi, > >My ffmpeg-based player plays a mpeg-ts file that downloaded from a >server. >I want my player be able to play the video file >even when it is being downloaded. > >There is no problem if the download speed is faster than reading speed, >otherwise, it just stop playing. >My question is that is there anyway to suspend ffmpeg file reading to >wait >for data available to proceed? > >Thanks >Jack > > > > >___ >Libav-user mailing list >Libav-user@ffmpeg.org >http://ffmpeg.org/mailman/listinfo/libav-user ___ Libav-user mailing list Libav-user@ffmpeg.org http://ffmpeg.org/mailman/listinfo/libav-user
Re: [Libav-user] get RGB values from ffmpeg frame
Have you looked at the tutorial concerning ffmpeg wit sdl, and/or the ffplay
sourcecode? Other things to check out would be the motion jpeg encoder - afaik
jpg images are in rgb space.
R
Navin wrote:
>Been trying these techniques, but I keep getting crashes. Help please?:
>
> avpicture_fill((AVPicture*) frame2, frame2_buffer,
>PIX_FMT_RGB24, width2, height2);
> //printf("data = %d, %d, %d, %d
>\n",frame2->data[0],frame2->data[1],frame2->data[2],frame2->data[3]);
> //printf("linesize = %d %d %d\n",frame2->linesize[0],
>frame2->linesize[1], frame2->linesize[2]);
> //printf("width = %d\n", pCodecCtx->width);
> //printf("height = %d\n", pCodecCtx->height);
> //std::cin.get();
>
> int linesize = frame2->linesize[0];
> for(int xx = 0; xx < (linesize * width1)-1; xx += 3)
> {
> int r = frame2->data[0][xx];//int r = frame2->data[0][xx];
> int g = frame2->data[0][xx+1];
> int b = frame2->data[0][xx+2];
> printf("xx=%d r=%d, g=%d, b=%d \n",xx, r,
>g, b);
> }
> printf("frame%d done",i++);
> //for(int xx = 0; xx < width1; xx = xx + 3)
> //{
> //for(int yy = 0; yy < height1; ++yy)
> //{
> ////int p = xx*3 + yy*frame2->linesize[0];
> ////int p = xx * 3 + yy * linesize;
> //printf("yy=%d xx=%d",yy,xx);
> //int p = yy * linesize + xx;
> //printf("p=%d\n",p);
> //int r = frame2->data[0][p];
> //int g = frame2->data[0][p+1];
> //int b = frame2->data[0][p+2];
> //printf("[r=%d, g=%d, b=%d ]\n", r, g, b);
> //}//for
> //}//for
>
>Nav
>
>On 11/20/2012 8:52 AM, Nav wrote:
>> Hi! Glad to be part of this mailing list.
>> What I wanted to create, was a program which would receive a
>streaming
>> video, and when it decodes a frame of the video into either a bitmap
>> format or just pure RGB (perhaps stored in a char array), it would
>> notify another program that it has received a frame, and the other
>> program would take the RGB values and display it.
>> I've already asked this question here:
>> http://ffmpeg.zeranoe.com/forum/viewtopic.php?f=15&t=805
>> and rogerdpack told me to post my question on the libav mailing list.
>> I have been through many websites, but they either use img_convert
>> (which doesn't work) or sws_scale, which crashes when I try to use it
>
>> with RGB.
>> Could anyone help with a complete piece of code which can give me the
>
>> RGB values of a frame?
>>
>> This is a part of the YUV conversion that I tried initially.
>>
>> i=0;
>> while(av_read_frame(pFormatCtx, &packet) >= 0)
>> {
>> // Is this a packet from the video stream?
>> if(packet.stream_index==videoStream)
>> {
>> // Decode video frame
>> avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished,
>&packet);
>>
>> // Did we get a video frame?
>> if(frameFinished)
>> {
>> // Convert the image into YUV format that SDL uses
>> sws_scale( sws_ctx, (uint8_t const * const *)pFrame->data,
>> pFrame->linesize, 0, pCodecCtx->height, pict.data, pict.linesize );
>>
>>
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