使用 FFMPEG 和 JNI 压缩视频 [英] Compress Videos using FFMPEG and JNI

问题描述

我想创建一个可以定位视频文件(超过 300 mb)并将其压缩为较小尺寸的 mp4 文件的 android 应用程序.

I want to create an android application which can locate a video file (which is more than 300 mb) and compress it to lower size mp4 file.

我已经尝试用 this

本教程非常有效，因为您正在压缩小尺寸视频(小于 100 mb)

This tutorial is a very effective since you 're compressing a small size video (below than 100 mb)

所以我尝试使用 JNI 来实现它.

So i tried to implement it using JNI .

我设法使用 this

但目前我想做的是压缩视频.我对 JNI 不是很了解.但我尝试使用以下 link

But currently what I want to do is to compress videos . I don't have very good knowledge on JNI. But i tried to understand it using following link

如果有人可以指导我使用 JNI 打开文件后压缩视频的步骤，那真是太棒了，谢谢

If some one can guide me the steps to compress video after open file it using JNI that whould really great , thanks

推荐答案

假设您已获得输入文件的 String 路径，我们可以相当轻松地完成您的任务.我假设您已经了解 NDK 基础知识:如何将本机 .c 文件连接到相应 .java 文件中的 native 方法(如果这是您的问题，请告诉我).相反，我将专注于如何在 Android/JNI 的上下文中使用 FFmpeg.

Assuming you've got the String path of the input file, we can accomplish your task fairly easily. I'll assume you have an understanding of the NDK basics: How to connect a native .c file to native methods in a corresponding .java file (Let me know if that's part of your question). Instead I'll focus on how to use FFmpeg within the context of Android / JNI.

高级概述:

#include <jni.h>
#include <android/log.h>
#include <string.h>
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"

#define LOG_TAG "FFmpegWrapper"
#define LOGI(...)  __android_log_print(ANDROID_LOG_INFO, LOG_TAG, __VA_ARGS__)
#define LOGE(...)  __android_log_print(ANDROID_LOG_ERROR, LOG_TAG, __VA_ARGS__)


void Java_com_example_yourapp_yourJavaClass_compressFile(JNIEnv *env, jobject obj, jstring jInputPath, jstring jInputFormat, jstring jOutputPath, jstring JOutputFormat){
  // One-time FFmpeg initialization
  av_register_all();
  avformat_network_init();
  avcodec_register_all();

  const char* inputPath = (*env)->GetStringUTFChars(env, jInputPath, NULL);
  const char* outputPath = (*env)->GetStringUTFChars(env, jOutputPath, NULL);
  // format names are hints. See available options on your host machine via $ ffmpeg -formats
  const char* inputFormat = (*env)->GetStringUTFChars(env, jInputFormat, NULL);
  const char* outputFormat = (*env)->GetStringUTFChars(env, jOutputFormat, NULL);

  AVFormatContext *outputFormatContext = avFormatContextForOutputPath(outputPath, outputFormat);
  AVFormatContext *inputFormatContext = avFormatContextForInputPath(inputPath, inputFormat /* not necessary since file can be inspected */);

  copyAVFormatContext(&outputFormatContext, &inputFormatContext);
  // Modify outputFormatContext->codec parameters per your liking
  // See http://ffmpeg.org/doxygen/trunk/structAVCodecContext.html

  int result = openFileForWriting(outputFormatContext, outputPath);
  if(result < 0){
      LOGE("openFileForWriting error: %d", result);
  }

  writeFileHeader(outputFormatContext);

  // Copy input to output frame by frame
  AVPacket *inputPacket;
  inputPacket = av_malloc(sizeof(AVPacket));

  int continueRecording = 1;
  int avReadResult = 0;
  int writeFrameResult = 0;
  int frameCount = 0;
  while(continueRecording == 1){
      avReadResult = av_read_frame(inputFormatContext, inputPacket);
      frameCount++;
      if(avReadResult != 0){
        if (avReadResult != AVERROR_EOF) {
            LOGE("av_read_frame error: %s", stringForAVErrorNumber(avReadResult));
        }else{
            LOGI("End of input file");
        }
        continueRecording = 0;
      }

      AVStream *outStream = outputFormatContext->streams[inputPacket->stream_index];
      writeFrameResult = av_interleaved_write_frame(outputFormatContext, inputPacket);
      if(writeFrameResult < 0){
          LOGE("av_interleaved_write_frame error: %s", stringForAVErrorNumber(avReadResult));
      }
  }

  // Finalize the output file
  int writeTrailerResult = writeFileTrailer(outputFormatContext);
  if(writeTrailerResult < 0){
      LOGE("av_write_trailer error: %s", stringForAVErrorNumber(writeTrailerResult));
  }
  LOGI("Wrote trailer");
}

有关所有辅助功能的完整内容(camelCase 中的功能)，请参阅我的完整项目 Github.有问题吗?我很乐意详细说明.

For the full content of all the auxillary functions (the ones in camelCase), see my full project on Github. Got questions? I'm happy to elaborate.

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