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• Aspect ratio problems at transcoding with ffmpeg [closed]

  19 novembre 2023, par udippel

  I have a huge collection of videos from the last 20+ years, videos in all sorts of formats. I use gerbera as open source UPnP-AV media server. Our TV handles only very limited of these formats. Therefore I use the transcoding feature of gerbera (I don't want to convert the 2000+ files ; thereby avoiding loss of multiple audio tracks, (multiple) subtitles, and so forth).

  


  This is my current unified argument line for ffmpeg :
-c:v mpeg2video -maxrate 20000k -vf setdar=16/9 -r 24000/1001 -qscale:v 4 -top 1 -c:a mp2 -f mpeg -y
It works pretty okay, except of the aspect ratios. Well, I don't understand this fully, because ffprobe for File A states :
Stream #0:0: Video: mpeg4 (Simple Profile) (XVID / 0x44495658), yuv420p, 624x464 [SAR 1:1 DAR 39:29], 1500 kb/s, 25 fps, 25 tbr, 25 tbn, 25 tbc
This file displays very well.
File B comes as :
Stream #0:0(eng): Video: h264 (High), yuv420p(tv, bt709, progressive), 960x720, SAR 1:1 DAR 4:3, 23.98 fps, 23.98 tbr, 1k tbn, 180k tbc (default)
This file displays horribly squeezed vertically and doesn't fill the screen left and right neither, with the same settings of the TV. Also, playing this file (and others, naturally) the TV doesn't offer the 14:9 display option, which is available e.g. for the file further up.

  


  Both have same SAR, DAR, almost identical H:V ratios (1.345, 1.333) ; and almost identical DAR.

  


  My questions :

  


  

  1. Why, despite of almost identical pixel ratios, DAR and SAR are these files handled so differently in one and the same session on the same TV (SONY), please ?

  


  2. With which method could I instruct ffmpeg to display the second file properly, too, please ?
(I have already tried 'scale' ; but to no avail. Which could have been foreseen, since the ratios are already very close.)
My guess is, that the (tv, bt709, progressive) mess things up.
(I have already tried to add the yuv420p in the argument line, also to no avail.)

  


  


  Appreciate any help,

  


  Uwe

  


  I have already tried to add a 'scale' option ; but to no avail. Which could have been foreseen, since the ratios are already very close.
I have already tried to add the yuv420p in the argument line, also to no avail.
I have already tried force_original_aspect_ratio, but also here, nothing improving.
Also, I played with -aspect, but the aspects are okay, and would need individual corrections, which I can't and don't to do for 2000+ files. A simple 16:9 doesn't cut it.

  


• ffmpeg memory leak when opening libx264 encoder

  18 octobre 2023, par ksb496

  I have spotted a memory leak issue when I use the libx264 encoder in the FFmpeg C API. Specifically, when it comes to deallocate memory after encoding a video. After tracking the factor that causes it, I realized that it happens after invoking avcodec_open2, which allocates some memory that afterwards cannot be freed. Once the video is processed, calling avcodec_close and then avcodec_free_context does not entirely free all the allocated memory.

  


  After some investigation, I found out that the problem could be located in AVCodecContext::priv_data being allocated but not being freed afterwards. In this question a solution to the issue is proposed. However, I tried to implement it without success (the memory being leaked seems to be exactly the same).

  


  As a matter of fact, the following simple code (which includes the patch that was proposed in the aforementioned question), in which the codec is being opened and closed multiple times without even writing a single frame or allocating an AVFormatContext, illustrates the memory leak.

  


  #include &#xA;extern "C"{&#xA;#include &#xA;#include <libavcodec></libavcodec>avcodec.h>&#xA;#include <libavutil></libavutil>opt.h>&#xA;}&#xA;&#xA;int main()&#xA;{&#xA;    avcodec_register_all();&#xA;&#xA;    AVCodec *codec;&#xA;    AVCodecContext *c;&#xA;    for (int n=0; n&lt;2000; n&#x2B;&#x2B;)&#xA;    {&#xA;        codec = avcodec_find_encoder_by_name("libx264");&#xA;        c=avcodec_alloc_context3(codec);&#xA;        c->pix_fmt=AV_PIX_FMT_YUV420P;&#xA;        c->width=1920;&#xA;        c->height=1080;&#xA;        c->time_base=(AVRational){1, 30};&#xA;        c->framerate=(AVRational){30, 1};&#xA;        avcodec_open2(c, codec, NULL);&#xA;        avcodec_close(c);&#xA;        av_opt_free(c->priv_data);&#xA;        av_freep(&amp;c->priv_data);&#xA;        avcodec_free_context(&amp;c);&#xA;    }&#xA;    return 0;&#xA;}&#xA;

  


  It must be remarked that if the line codec = avcodec_find_encoder_by_name("libx264") is replaced to an invocation to an internal/native encoder, e.g., codec = avcodec_find_encoder(AV_CODEC_ID_MPEG4), then the memory leak issue completely disappears. Hence, it certainly seems to be an issue related to some private data of the external encoder not being properly freed.

  


  It is also worth mentioning that I am using an old version of ffmpeg and libx264. To be more precise, ffmpeg version 2.8git and libx264 version 0.136.x. For technical reasons that are beyond the scope of this question, it is not possible to upgrade the libraries to newer versions onto the project in which these are being used. I am fully aware that most of the involved ffmpeg/libx264 code has been probably changed along the years and many functions became deprecated or fixed, and thus reporting this as a possible bug in the ffmpeg developer's mailbox is out of the question.

  


  Nevertheless, I am still asking this here because I would like to know whether it is just some mistake on my end and/or something I am not taking into account when it comes to free all the memory relative to an external encoder (best case scenario). Otherwise, I would like to know whether there can be some reasonably cheap solution through some custom code or function that can be implemented as a patch (assuming it is indeed an issue related to ffmpeg/libx264), no matter if it makes the whole deallocation code less elegant or concise. If someone is still working on these older versions of ffmpeg and can come up with a workaround, that would be highly appreciated.

  


• ffmpeg memory leak when opening libx264 encoder

  18 octobre 2023, par ksb496

  I have spotted a memory leak issue when I use the libx264 encoder in the FFmpeg C API. Specifically, when it comes to deallocate memory after encoding a video. After tracking the factor that causes it, I realized that it happens after invoking avcodec_open2, which allocates some memory that afterwards cannot be freed. Once the video is processed, calling avcodec_close and then avcodec_free_context does not entirely free all the allocated memory.

  


  After some investigation, I found out that the problem could be located in AVCodecContext::priv_data being allocated but not being freed afterwards. In this question a solution to the issue is proposed. However, I tried to implement it without success (the memory being leaked seems to be exactly the same).

  


  As a matter of fact, the following simple code (which includes the patch that was proposed in the aforementioned question), in which the codec is being opened and closed multiple times without even writing a single frame or allocating an AVFormatContext, illustrates the memory leak.

  


  #include &#xA;extern "C"{&#xA;#include &#xA;#include <libavcodec></libavcodec>avcodec.h>&#xA;#include <libavutil></libavutil>opt.h>&#xA;}&#xA;&#xA;int main()&#xA;{&#xA;    avcodec_register_all();&#xA;&#xA;    AVCodec *codec;&#xA;    AVCodecContext *c;&#xA;    for (int n=0; n&lt;2000; n&#x2B;&#x2B;)&#xA;    {&#xA;        codec = avcodec_find_encoder_by_name("libx264");&#xA;        c=avcodec_alloc_context3(codec);&#xA;        c->pix_fmt=AV_PIX_FMT_YUV420P;&#xA;        c->width=1920;&#xA;        c->height=1080;&#xA;        c->time_base=(AVRational){1, 30};&#xA;        c->framerate=(AVRational){30, 1};&#xA;        avcodec_open2(c, codec, NULL);&#xA;        avcodec_close(c);&#xA;        av_opt_free(c->priv_data);&#xA;        av_freep(&amp;c->priv_data);&#xA;        avcodec_free_context(&amp;c);&#xA;    }&#xA;    return 0;&#xA;}&#xA;

  


  It must be remarked that if the line codec = avcodec_find_encoder_by_name("libx264") is replaced to an invocation to an internal/native encoder, e.g., codec = avcodec_find_encoder(AV_CODEC_ID_MPEG4), then the memory leak issue completely disappears. Hence, it certainly seems to be an issue related to some private data of the external encoder not being properly freed.

  


  It is also worth mentioning that I am using an old version of ffmpeg and libx264. To be more precise, ffmpeg version 2.8git and libx264 version 0.136.x. For technical reasons that are beyond the scope of this question, it is not possible to upgrade the libraries to newer versions onto the project in which these are being used. I am fully aware that most of the involved ffmpeg/libx264 code has been probably changed along the years and many functions became deprecated or fixed, and thus reporting this as a possible bug in the ffmpeg developer's mailbox is out of the question.

  


  Nevertheless, I am still asking this here because I would like to know whether it is just some mistake on my end and/or something I am not taking into account when it comes to free all the memory relative to an external encoder (best case scenario). Otherwise, I would like to know whether there can be some reasonably cheap solution through some custom code or function that can be implemented as a patch (assuming it is indeed an issue related to ffmpeg/libx264), no matter if it makes the whole deallocation code less elegant or concise. If someone is still working on these older versions of ffmpeg and can come up with a workaround, that would be highly appreciated.