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The Slip - Artworks
26 septembre 2011, par
Mis à jour : Septembre 2011
Langue : English
Type : Texte
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Podcasting Legal guide
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Mis à jour : Mai 2011
Langue : English
Type : Texte
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Creativecommons informational flyer
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Mis à jour : Juillet 2013
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Sur d’autres sites (4608)
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Why does the frame count change when scaling with FFmpeg ?
22 octobre 2016, par ajmicekI use this to scale 1920x1080 H.264 videos :
ffmpeg -i IMG_1438.MOV -threads 2 -vf scale=-2:600 IMG_1438_scaledTo600.MOVAnd it works great ! But here is my question : most of the time, the frame rate stays exactly the same between the original file and the scaled file. For example :
$ mediainfo -F IMG_1426.MOV | grep Frame\ rate
Frame rate : 29.970
Frame rate : 29.970 FPS
Frame rate mode : VFR
Frame rate mode : Variable
Frame rate : 29.970
Frame rate : 29.970 (29970/1000) FPS
$ mediainfo -F IMG_1426_scaledTo600.MOV | grep Frame\ rate
Frame rate : 29.970
Frame rate : 29.970 FPS
Frame rate mode : CFR
Frame rate mode : Constant
Frame rate : 29.970
Frame rate : 29.970 (30000/1001) FPSBut sometimes, the frame rate increases dramatically :
$ mediainfo -F IMG_1438.MOV | grep Frame\ rate
Frame rate : 25.044
Frame rate : 25.044 FPS
Frame rate mode : VFR
Frame rate mode : Variable
Frame rate : 25.044
Frame rate : 25.044 FPS
$ mediainfo -F IMG_1438_scaledTo600.MOV | grep Frame\ rate
Frame rate : 120.000
Frame rate : 120.000 FPS
Frame rate mode : CFR
Frame rate mode : Constant
Frame rate : 120.000
Frame rate : 120.000 FPSWhat should I know about FFmpeg or libx264 or libswscale that will help me understand why this happens ? (Hoping to hear from LordNeckbeard, in particular).
mediainfo IMG_1438.MOV --Fulloutputs :General
Count : 327
Count of stream of this kind : 1
Kind of stream : General
Kind of stream : General
Stream identifier : 0
Count of video streams : 1
Count of audio streams : 1
OtherCount : 2
Video_Format_List : AVC
Video_Format_WithHint_List : AVC
Codecs Video : AVC
Audio_Format_List : AAC
Audio_Format_WithHint_List : AAC
Audio codecs : AAC LC
Complete name : IMG_1438.MOV
File name : IMG_1438
File extension : MOV
Format : MPEG-4
Format : MPEG-4
Format/Extensions usually used : mp4 m4v m4a m4b m4p 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma f4v
Commercial name : MPEG-4
Format profile : QuickTime
Internet media type : video/mp4
Codec ID : qt
Codec ID : qt 0000.00 (qt )
Codec ID/Url : http://www.apple.com/quicktime/download/standalone.html
CodecID_Version : 0000.00
CodecID_Compatible : qt
Codec : MPEG-4
Codec : MPEG-4
Codec/Extensions usually used : mp4 m4v m4a m4b m4p 3gpp 3gp 3gpp2 3g2 k3g jpm jpx mqv ismv isma f4v
File size : 113990140
File size : 109 MiB
File size : 109 MiB
File size : 109 MiB
File size : 109 MiB
File size : 108.7 MiB
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52:09
Duration : 00:00:52.268 (00:00:52:09)
Overall bit rate : 17447026
Overall bit rate : 17.4 Mb/s
Frame rate : 25.044
Frame rate : 25.044 FPS
Frame count : 1309
Stream size : 56670
Stream size : 55.3 KiB (0%)
Stream size : 55 KiB
Stream size : 55 KiB
Stream size : 55.3 KiB
Stream size : 55.34 KiB
Stream size : 55.3 KiB (0%)
Proportion of this stream : 0.00050
HeaderSize : 28
DataSize : 113966271
FooterSize : 23841
IsStreamable : No
Encoded date : UTC 2016-10-08 22:51:19
Tagged date : UTC 2016-10-08 22:52:12
File last modification date : UTC 2016-10-08 22:51:19
File last modification date (local) : 2016-10-08 17:51:19
Writing library : Apple QuickTime
Writing library : Apple QuickTime
Encoded_Library_Name : Apple QuickTime
com.apple.quicktime.make : Apple
com.apple.quicktime.model : iPhone 5
com.apple.quicktime.software : 10.0.2
com.apple.quicktime.creationdate : 2016-10-08T17:51:19-0500
Video
Count : 334
Count of stream of this kind : 1
Kind of stream : Video
Kind of stream : Video
Stream identifier : 0
StreamOrder : 0
ID : 1
ID : 1
Format : AVC
Format/Info : Advanced Video Codec
Format/Url : http://developers.videolan.org/x264.html
Commercial name : AVC
Format profile : High@L4.1
Format settings : CABAC / 1 Ref Frames
Format settings, CABAC : Yes
Format settings, CABAC : Yes
Format settings, ReFrames : 1
Format settings, ReFrames : 1 frame
Internet media type : video/H264
Codec ID : avc1
Codec ID/Info : Advanced Video Coding
Codec ID/Url : http://www.apple.com/quicktime/download/standalone.html
Codec : AVC
Codec : AVC
Codec/Family : AVC
Codec/Info : Advanced Video Codec
Codec/Url : http://developers.videolan.org/x264.html
Codec/CC : avc1
Codec profile : High@L4.1
Codec settings : CABAC / 1 Ref Frames
Codec settings, CABAC : Yes
Codec_Settings_RefFrames : 1
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52:09
Duration : 00:00:52.268 (00:00:52:09)
Bit rate : 17375530
Bit rate : 17.4 Mb/s
Width : 1920
Width : 1 920 pixels
Height : 1080
Height : 1 080 pixels
Stored_Height : 1088
Sampled_Width : 1920
Sampled_Height : 1080
Pixel aspect ratio : 1.000
Display aspect ratio : 1.778
Display aspect ratio : 16:9
Rotation : 90.000
Rotation : 90°
Frame rate mode : VFR
Frame rate mode : Variable
Frame rate : 25.044
Frame rate : 25.044 FPS
Minimum frame rate : 23.077
Minimum frame rate : 23.077 FPS
Maximum frame rate : 30.000
Maximum frame rate : 30.000 FPS
Frame count : 1309
Resolution : 8
Resolution : 8 bits
Colorimetry : 4:2:0
Color space : YUV
Chroma subsampling : 4:2:0
Chroma subsampling : 4:2:0
Bit depth : 8
Bit depth : 8 bits
Scan type : Progressive
Scan type : Progressive
Interlacement : PPF
Interlacement : Progressive
Bits/(Pixel*Frame) : 0.335
Stream size : 113523046
Stream size : 108 MiB (100%)
Stream size : 108 MiB
Stream size : 108 MiB
Stream size : 108 MiB
Stream size : 108.3 MiB
Stream size : 108 MiB (100%)
Proportion of this stream : 0.99590
Title : Core Media Video
Encoded date : UTC 2016-10-08 22:51:19
Tagged date : UTC 2016-10-08 22:52:12
Color range : Limited
colour_description_present : Yes
Color primaries : BT.709
Transfer characteristics : BT.709
Matrix coefficients : BT.709
Audio
Count : 272
Count of stream of this kind : 1
Kind of stream : Audio
Kind of stream : Audio
Stream identifier : 0
StreamOrder : 1
ID : 2
ID : 2
Format : AAC
Format/Info : Advanced Audio Codec
Commercial name : AAC
Format profile : LC
Codec ID : 40
Codec : AAC LC
Codec : AAC LC
Codec/Family : AAC
Codec/CC : 40
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52:15
Duration : 00:00:52.268 (00:00:52:15)
Source duration : 52338
Source duration : 52 s 338 ms
Source duration : 52 s 338 ms
Source duration : 52 s 338 ms
Source duration : 00:00:52.338
Bit rate mode : CBR
Bit rate mode : Constant
Bit rate : 64000
Bit rate : 64.0 kb/s
Channel(s) : 1
Channel(s) : 1 channel
Channel positions : Front: C
Channel positions : 1/0/0
ChannelLayout : C
Samples per frame : 1024
Sampling rate : 44100
Sampling rate : 44.1 kHz
Samples count : 2305019
Frame rate : 43.066
Frame rate : 43.066 FPS (1024 spf)
Frame count : 2251
Source frame count : 2254
Compression mode : Lossy
Compression mode : Lossy
Stream size : 410424
Stream size : 401 KiB (0%)
Stream size : 401 KiB
Stream size : 401 KiB
Stream size : 401 KiB
Stream size : 400.8 KiB
Stream size : 401 KiB (0%)
Proportion of this stream : 0.00360
Source stream size : 410894
Source stream size : 401 KiB (0%)
Source stream size : 401 KiB
Source stream size : 401 KiB
Source stream size : 401 KiB
Source stream size : 401.3 KiB
Source stream size : 401 KiB (0%)
Source_StreamSize_Proportion : 0.00360
Title : Core Media Audio
Encoded date : UTC 2016-10-08 22:51:19
Tagged date : UTC 2016-10-08 22:52:12
Other #1
Count : 112
Count of stream of this kind : 2
Kind of stream : Other
Kind of stream : Other
Stream identifier : 0
Stream identifier : 1
Type : meta
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52.268
Frame count : 6
Bit rate mode : VBR
Other #2
Count : 112
Count of stream of this kind : 2
Kind of stream : Other
Kind of stream : Other
Stream identifier : 1
Stream identifier : 2
Type : meta
Duration : 52268
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 52 s 268 ms
Duration : 00:00:52.268
Duration : 00:00:52.268
Frame count : 1
Bit rate mode : CBRand
ffprobe IMG_1438.MOVoutputs :ffprobe version 3.1.3 Copyright (c) 2007-2016 the FFmpeg developers
built with Apple LLVM version 7.3.0 (clang-703.0.31)
configuration: --prefix=/usr/local/Cellar/ffmpeg/3.1.3 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-opencl --enable-libx264 --enable-libmp3lame --enable-libxvid --disable-lzma --enable-vda
libavutil 55. 28.100 / 55. 28.100
libavcodec 57. 48.101 / 57. 48.101
libavformat 57. 41.100 / 57. 41.100
libavdevice 57. 0.101 / 57. 0.101
libavfilter 6. 47.100 / 6. 47.100
libavresample 3. 0. 0 / 3. 0. 0
libswscale 4. 1.100 / 4. 1.100
libswresample 2. 1.100 / 2. 1.100
libpostproc 54. 0.100 / 54. 0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'IMG_1438.MOV':
Metadata:
major_brand : qt
minor_version : 0
compatible_brands: qt
creation_time : 2016-10-08 22:51:19
com.apple.quicktime.make: Apple
com.apple.quicktime.model: iPhone 5
com.apple.quicktime.software: 10.0.2
com.apple.quicktime.creationdate: 2016-10-08T17:51:19-0500
Duration: 00:00:52.27, start: 0.000000, bitrate: 17446 kb/s
Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080, 17375 kb/s, 25.04 fps, 120 tbr, 600 tbn, 1200 tbc (default)
Metadata:
rotate : 90
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
encoder : H.264
Side data:
displaymatrix: rotation of -90.00 degrees
Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 62 kb/s (default)
Metadata:
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
Stream #0:2(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
Metadata:
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
Stream #0:3(und): Data: none (mebx / 0x7862656D), 0 kb/s (default)
Metadata:
creation_time : 2016-10-08 22:51:19
handler_name : Core Media Data Handler
Unsupported codec with id 0 for input stream 2
Unsupported codec with id 0 for input stream 3UPDATE
To clarify : my video above, the one with the high framerate (120 FPS) output after scaling, plays perfectly before and after scaling with FFmpeg (no sync issues, and 120 FPS is only about 14% larger in file size), I am simply trying to understand why this increase in framerate happens (just a little beyond Mulvya’s note that the framerate stored in the container is wrong).From a programming perspective, the initial issue I ran into was that I was using
frame=from FFmpeg’s sterr console output to determine progress, which reports erroneous results when the frame count increases dramatically on output ("I’m 372% done encoding ?!") ; I have since read another stackoverflow answer and changed my code to usetime=, which appears to be a more robust way for me to display FFmpeg progress. (Also, there is FFmpeg’s-progressoption, of course).Improving on the original command
My new command to scale, preserve a useful framerate, and optimize threads :
ffmpeg -i IMG_1438.MOV -vf scale=-2:600 -r 30 -vsync 0 IMG_1438_scaledTo600.MOVWhere
30is the "Maximum frame rate" frommediainfo.Thanks to help in the comments, I now know I do not fully understand FFmpeg’s use of three different time bases for timestamps :
tbn,tbc, andtbr.
They were explained by Robert Swain in 2009 and his explanation was also used to answer a Stackoverflow question about tbn, tbc, tbr.It sounds to me, as I’m pulling together comments from Mulvya below and Michael Rampe at another forum, that
tbris guessed ; it is frequently but not always the best value to use when changing from a variable to a constant frame rate video.Which leaves these 2 questions...
(1)
tbris incorrect when "field rate and frame rate" differ ? Does this happen a lot ?
(2) Is-r 30where30is the maximum frame rate reported bymediainfothe best way to do it for most codec/container combinations ? (Or should I only use this method when I am scaling a H.264/MPEG-4 AVC video ?) -
Libav (ffmpeg) copying decoded video timestamps to encoder
31 octobre 2016, par Jason CI am writing an application that decodes a single video stream from an input file (any codec, any container), does a bunch of image processing, and encodes the results to an output file (single video stream, Quicktime RLE, MOV). I am using ffmpeg’s libav 3.1.5 (Windows build for now, but the application will be cross-platform).
There is a 1:1 correspondence between input and output frames and I want the frame timing in the output to be identical to the input. I am having a really, really hard time accomplishing this. So my general question is : How do I reliably (as in, in all cases of inputs) set the output frame timing identical to the input ?
It took me a very long time to slog through the API and get to the point I am at now. I put together a minimal test program to work with :
#include <cstdio>
extern "C" {
#include <libavcodec></libavcodec>avcodec.h>
#include <libavformat></libavformat>avformat.h>
#include <libavutil></libavutil>avutil.h>
#include <libavutil></libavutil>imgutils.h>
#include <libswscale></libswscale>swscale.h>
}
using namespace std;
struct DecoderStuff {
AVFormatContext *formatx;
int nstream;
AVCodec *codec;
AVStream *stream;
AVCodecContext *codecx;
AVFrame *rawframe;
AVFrame *rgbframe;
SwsContext *swsx;
};
struct EncoderStuff {
AVFormatContext *formatx;
AVCodec *codec;
AVStream *stream;
AVCodecContext *codecx;
};
template <typename t="t">
static void dump_timebase (const char *what, const T *o) {
if (o)
printf("%s timebase: %d/%d\n", what, o->time_base.num, o->time_base.den);
else
printf("%s timebase: null object\n", what);
}
// reads next frame into d.rawframe and d.rgbframe. returns false on error/eof.
static bool read_frame (DecoderStuff &d) {
AVPacket packet;
int err = 0, haveframe = 0;
// read
while (!haveframe && err >= 0 && ((err = av_read_frame(d.formatx, &packet)) >= 0)) {
if (packet.stream_index == d.nstream) {
err = avcodec_decode_video2(d.codecx, d.rawframe, &haveframe, &packet);
}
av_packet_unref(&packet);
}
// error output
if (!haveframe && err != AVERROR_EOF) {
char buf[500];
av_strerror(err, buf, sizeof(buf) - 1);
buf[499] = 0;
printf("read_frame: %s\n", buf);
}
// convert to rgb
if (haveframe) {
sws_scale(d.swsx, d.rawframe->data, d.rawframe->linesize, 0, d.rawframe->height,
d.rgbframe->data, d.rgbframe->linesize);
}
return haveframe;
}
// writes an output frame, returns false on error.
static bool write_frame (EncoderStuff &e, AVFrame *inframe) {
// see note in so post about outframe here
AVFrame *outframe = av_frame_alloc();
outframe->format = inframe->format;
outframe->width = inframe->width;
outframe->height = inframe->height;
av_image_alloc(outframe->data, outframe->linesize, outframe->width, outframe->height,
AV_PIX_FMT_RGB24, 1);
//av_frame_copy(outframe, inframe);
static int count = 0;
for (int n = 0; n < outframe->width * outframe->height; ++ n) {
outframe->data[0][n*3+0] = ((n+count) % 100) ? 0 : 255;
outframe->data[0][n*3+1] = ((n+count) % 100) ? 0 : 255;
outframe->data[0][n*3+2] = ((n+count) % 100) ? 0 : 255;
}
++ count;
AVPacket packet;
av_init_packet(&packet);
packet.size = 0;
packet.data = NULL;
int err, havepacket = 0;
if ((err = avcodec_encode_video2(e.codecx, &packet, outframe, &havepacket)) >= 0 && havepacket) {
packet.stream_index = e.stream->index;
err = av_interleaved_write_frame(e.formatx, &packet);
}
if (err < 0) {
char buf[500];
av_strerror(err, buf, sizeof(buf) - 1);
buf[499] = 0;
printf("write_frame: %s\n", buf);
}
av_packet_unref(&packet);
av_freep(&outframe->data[0]);
av_frame_free(&outframe);
return err >= 0;
}
int main (int argc, char *argv[]) {
const char *infile = "wildlife.wmv";
const char *outfile = "test.mov";
DecoderStuff d = {};
EncoderStuff e = {};
av_register_all();
// decoder
avformat_open_input(&d.formatx, infile, NULL, NULL);
avformat_find_stream_info(d.formatx, NULL);
d.nstream = av_find_best_stream(d.formatx, AVMEDIA_TYPE_VIDEO, -1, -1, &d.codec, 0);
d.stream = d.formatx->streams[d.nstream];
d.codecx = avcodec_alloc_context3(d.codec);
avcodec_parameters_to_context(d.codecx, d.stream->codecpar);
avcodec_open2(d.codecx, NULL, NULL);
d.rawframe = av_frame_alloc();
d.rgbframe = av_frame_alloc();
d.rgbframe->format = AV_PIX_FMT_RGB24;
d.rgbframe->width = d.codecx->width;
d.rgbframe->height = d.codecx->height;
av_frame_get_buffer(d.rgbframe, 1);
d.swsx = sws_getContext(d.codecx->width, d.codecx->height, d.codecx->pix_fmt,
d.codecx->width, d.codecx->height, AV_PIX_FMT_RGB24,
SWS_POINT, NULL, NULL, NULL);
//av_dump_format(d.formatx, 0, infile, 0);
dump_timebase("in stream", d.stream);
dump_timebase("in stream:codec", d.stream->codec); // note: deprecated
dump_timebase("in codec", d.codecx);
// encoder
avformat_alloc_output_context2(&e.formatx, NULL, NULL, outfile);
e.codec = avcodec_find_encoder(AV_CODEC_ID_QTRLE);
e.stream = avformat_new_stream(e.formatx, e.codec);
e.codecx = avcodec_alloc_context3(e.codec);
e.codecx->bit_rate = 4000000; // arbitrary for qtrle
e.codecx->width = d.codecx->width;
e.codecx->height = d.codecx->height;
e.codecx->gop_size = 30; // 99% sure this is arbitrary for qtrle
e.codecx->pix_fmt = AV_PIX_FMT_RGB24;
e.codecx->time_base = d.stream->time_base; // ???
e.codecx->flags |= (e.formatx->flags & AVFMT_GLOBALHEADER) ? AV_CODEC_FLAG_GLOBAL_HEADER : 0;
avcodec_open2(e.codecx, NULL, NULL);
avcodec_parameters_from_context(e.stream->codecpar, e.codecx);
//av_dump_format(e.formatx, 0, outfile, 1);
dump_timebase("out stream", e.stream);
dump_timebase("out stream:codec", e.stream->codec); // note: deprecated
dump_timebase("out codec", e.codecx);
// open file and write header
avio_open(&e.formatx->pb, outfile, AVIO_FLAG_WRITE);
avformat_write_header(e.formatx, NULL);
// frames
while (read_frame(d) && write_frame(e, d.rgbframe))
;
// write trailer and close file
av_write_trailer(e.formatx);
avio_closep(&e.formatx->pb);
}
</typename></cstdio>A few notes about that :
- Since all of my attempts at frame timing so far have failed, I’ve removed almost all timing-related stuff from this code to start with a clean slate.
- Almost all error checking and cleanup omitted for brevity.
- The reason I allocate a new output frame with a new buffer in
write_frame, rather than usinginframedirectly, is because this is more representative of what my real application is doing. My real app also uses RGB24 internally, hence the conversions here. - The reason I generate a weird pattern in
outframe, rather than using e.g.av_copy_frame, is because I just wanted a test pattern that compressed well with Quicktime RLE (my test input ends up generating a 1.7GB output file otherwise). - The input video I am using, "wildlife.wmv", can be found here. I’ve hard-coded the filenames.
- I am aware that
avcodec_decode_video2andavcodec_encode_video2are deprecated, but don’t care. They work fine, I’ve already struggled too much getting my head around the latest version of the API, ffmpeg changes their API with nearly every release, and I really don’t feel like dealing withavcodec_send_*andavcodec_receive_*right now. - I think I’m supposed to be finishing off by passing a NULL frame to
avcodec_encode_video2to flush some buffers or something but I’m a bit confused about that. Unless somebody feels like explaining that let’s ignore it for now, it’s a separate question. The docs are as vague about this point as they are about everything else. - My test input file’s frame rate is 29.97.
Now, as for my current attempts. The following timing related fields are present in the above code, with details/confusion in bold. There’s a lot of them, because the API is mind-bogglingly convoluted :
main: d.stream->time_base: Input video stream time base. For my test input file this is 1/1000.main: d.stream->codec->time_base: Not sure what this is (I never could make sense of whyAVStreamhas anAVCodecContextfield when you always use your own new context anyways) and also thecodecfield is deprecated. For my test input file this is 1/1000.main: d.codecx->time_base: Input codec context time-base. For my test input file this is 0/1. Am I supposed to set it ?main: e.stream->time_base: Time base of the output stream I create. What do I set this to ?main: e.stream->codec->time_base: Time base of the deprecated and mysterious codec field of the output stream I create. Do I set this to anything ?main: e.codecx->time_base: Time base of the encoder context I create. What do I set this to ?read_frame: packet.dts: Decoding timestamp of packet read.read_frame: packet.pts: Presentation timestamp of packet read.read_frame: packet.duration: Duration of packet read.read_frame: d.rawframe->pts: Presentation timestamp of raw frame decoded. This is always 0. Why isn’t it read by the decoder...?read_frame: d.rgbframe->pts/write_frame: inframe->pts: Presentation timestamp of decoded frame converted to RGB. Not set to anything currently.read_frame: d.rawframe->pkt_*: Fields copied from packet, discovered after reading this post. They are set correctly but I don’t know if they are useful.write_frame: outframe->pts: Presentation timestamp of frame being encoded. Should I set this to something ?write_frame: outframe->pkt_*: Timing fields from a packet. Should I set these ? They seem to be ignored by the encoder.write_frame: packet.dts: Decoding timestamp of packet being encoded. What do I set it to ?write_frame: packet.pts: Presentation timestamp of packet being encoded. What do I set it to ?write_frame: packet.duration: Duration of packet being encoded. What do I set it to ?
I have tried the following, with the described results. Note that
inframeisd.rgbframe:-
- Init
e.stream->time_base = d.stream->time_base - Init
e.codecx->time_base = d.codecx->time_base - Set
d.rgbframe->pts = packet.dtsinread_frame - Set
outframe->pts = inframe->ptsinwrite_frame - Result : Warning that encoder time base is not set (since
d.codecx->time_base was 0/1), seg fault.
- Init
-
- Init
e.stream->time_base = d.stream->time_base - Init
e.codecx->time_base = d.stream->time_base - Set
d.rgbframe->pts = packet.dtsinread_frame - Set
outframe->pts = inframe->ptsinwrite_frame - Result : No warnings, but VLC reports frame rate as 480.048 (no idea where this number came from) and file plays too fast.
Also the encoder sets all the timing fields in(Edit : Turns out this is becausepacketto 0, which was not what I expected.av_interleaved_write_frame, unlikeav_write_frame, takes ownership of the packet and swaps it with a blank one, and I was printing the values after that call. So they are not ignored.)
- Init
-
- Init
e.stream->time_base = d.stream->time_base - Init
e.codecx->time_base = d.stream->time_base - Set
d.rgbframe->pts = packet.dtsinread_frame - Set any of pts/dts/duration in
packetinwrite_frameto anything. - Result : Warnings about packet timestamps not set. Encoder seems to reset all packet timing fields to 0, so none of this has any effect.
- Init
-
- Init
e.stream->time_base = d.stream->time_base - Init
e.codecx->time_base = d.stream->time_base - I found these fields,
pkt_pts,pkt_dts, andpkt_durationinAVFrameafter reading this post, so I tried copying those all the way through tooutframe. - Result : Really had my hopes up, but ended up with same results as attempt 3 (packet timestamp not set warning, incorrect results).
- Init
I tried various other hand-wavey permutations of the above and nothing worked. What I want to do is create an output file that plays back with the same timing and frame rate as the input (29.97 constant frame rate in this case).
So how do I do this ? Of the zillions of timing related fields here, what do I do to make the output be the same as the input ? And how do I do it in such a way that handles arbitrary video input formats that may store their time stamps and time bases in different places ? I need this to always work.
For reference, here is a table of all the packet and frame timestamps read from the video stream of my test input file, to give a sense of what my test file looks like. None of the input packet pts’ are set, same with frame pts, and for some reason the duration of the first 108 frames is 0. VLC plays the file fine and reports the frame rate as 29.9700089 :
- Table is here since it was too large for this post.
-
ffmpeg - convert image sequence to video with reversed order
8 avril 2017, par 0__Looking at the docs, it is not apparent to me whether ffmpeg would allow me to convert an image sequence to a video in reverse order, for example using this sequence :
frame-1000.jpg
frame-999.jpg
frame-998.jpg
...
frame-1.jpgIs it possible to give a "step direction" for the frame indices ?
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