视频的横竖问题

我们系统中用户上传到视频多数是客户用手机拍摄的，现在存在一个问题，就是PC浏览器上播放的时候，这个视频是横着的。
大家明白我的意思吗？ 实际事物是： 1，但是视频看起来就是： 一 。

现在我想把视频变成是跟实际事物一直的状态。

七牛返回的视频元信息中有rotate:90这样的参数，还有高度和宽度。

我的想法：
1、判断高度和宽度，全部转为高>宽
2、我对rotate这个参数不太理解，这个能代表实际和视频的角度差吗？ （百度上出来的全部是imagerotate()，没有视频方面的。ffmpeg也没有提到这个，只是说了一些截图之类的问题。）

考虑到有些视频就是手机横着拍摄的，强制转了不是又出现了偏差？

求助有什么办法可以解决这个问题

我提供一个视频的元信息，大家帮我看看咯，谢谢

streams[1].tags.rotate "rotate": "90",

<code>{
    "streams": [
        {
            "index": 0,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "LC",
            "codec_type": "audio",
            "codec_time_base": "1/44100",
            "codec_tag_string": "mp4a",
            "codec_tag": "0x6134706d",
            "sample_fmt": "fltp",
            "sample_rate": "44100",
            "channels": 1,
            "channel_layout": "mono",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/44100",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 2408448,
            "duration": "54.613333",
            "bit_rate": "89406",
            "nb_frames": "2352",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0
            },
            "tags": {
                "creation_time": "2015-11-08 14:36:49",
                "language": "und",
                "handler_name": "Core Media Audio"
            }
        },
        {
            "index": 1,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "Main",
            "codec_type": "video",
            "codec_time_base": "1/1200",
            "codec_tag_string": "avc1",
            "codec_tag": "0x31637661",
            "width": 480,
            "height": 272,
            "has_b_frames": 0,
            "sample_aspect_ratio": "0:1",
            "display_aspect_ratio": "0:1",
            "pix_fmt": "yuv420p",
            "level": 21,
            "color_range": "tv",
            "color_space": "bt709",
            "color_transfer": "bt709",
            "color_primaries": "bt709",
            "chroma_location": "left",
            "is_avc": "1",
            "nal_length_size": "4",
            "r_frame_rate": "30000/1001",
            "avg_frame_rate": "490800/16369",
            "time_base": "1/600",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 32738,
            "duration": "54.563333",
            "bit_rate": "710127",
            "bits_per_raw_sample": "8",
            "nb_frames": "1636",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0
            },
            "tags": {
                "rotate": "90",
                "creation_time": "2015-11-08 14:36:49",
                "language": "und",
                "handler_name": "Core Media Video"
            }
        }
    ],
    "format": {
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
        "format_long_name": "QuickTime / MOV",
        "start_time": "0.000000",
        "duration": "54.563333",
        "size": "5488167",
        "bit_rate": "804667",
        "probe_score": 100,
        "tags": {
            "major_brand": "mp42",
            "minor_version": "1",
            "compatible_brands": "mp41mp42isom",
            "creation_time": "2015-11-08 14:36:49"
        }
    }
}</code>

回复内容：

我们系统中用户上传到视频多数是客户用手机拍摄的，现在存在一个问题，就是PC浏览器上播放的时候，这个视频是横着的。
大家明白我的意思吗？ 实际事物是： 1，但是视频看起来就是： 一 。

现在我想把视频变成是跟实际事物一直的状态。

七牛返回的视频元信息中有rotate:90这样的参数，还有高度和宽度。

我的想法：
1、判断高度和宽度，全部转为高>宽
2、我对rotate这个参数不太理解，这个能代表实际和视频的角度差吗？ （百度上出来的全部是imagerotate()，没有视频方面的。ffmpeg也没有提到这个，只是说了一些截图之类的问题。）

考虑到有些视频就是手机横着拍摄的，强制转了不是又出现了偏差？

求助有什么办法可以解决这个问题

我提供一个视频的元信息，大家帮我看看咯，谢谢

streams[1].tags.rotate "rotate": "90",

<code>{
    "streams": [
        {
            "index": 0,
            "codec_name": "aac",
            "codec_long_name": "AAC (Advanced Audio Coding)",
            "profile": "LC",
            "codec_type": "audio",
            "codec_time_base": "1/44100",
            "codec_tag_string": "mp4a",
            "codec_tag": "0x6134706d",
            "sample_fmt": "fltp",
            "sample_rate": "44100",
            "channels": 1,
            "channel_layout": "mono",
            "bits_per_sample": 0,
            "r_frame_rate": "0/0",
            "avg_frame_rate": "0/0",
            "time_base": "1/44100",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 2408448,
            "duration": "54.613333",
            "bit_rate": "89406",
            "nb_frames": "2352",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0
            },
            "tags": {
                "creation_time": "2015-11-08 14:36:49",
                "language": "und",
                "handler_name": "Core Media Audio"
            }
        },
        {
            "index": 1,
            "codec_name": "h264",
            "codec_long_name": "H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10",
            "profile": "Main",
            "codec_type": "video",
            "codec_time_base": "1/1200",
            "codec_tag_string": "avc1",
            "codec_tag": "0x31637661",
            "width": 480,
            "height": 272,
            "has_b_frames": 0,
            "sample_aspect_ratio": "0:1",
            "display_aspect_ratio": "0:1",
            "pix_fmt": "yuv420p",
            "level": 21,
            "color_range": "tv",
            "color_space": "bt709",
            "color_transfer": "bt709",
            "color_primaries": "bt709",
            "chroma_location": "left",
            "is_avc": "1",
            "nal_length_size": "4",
            "r_frame_rate": "30000/1001",
            "avg_frame_rate": "490800/16369",
            "time_base": "1/600",
            "start_pts": 0,
            "start_time": "0.000000",
            "duration_ts": 32738,
            "duration": "54.563333",
            "bit_rate": "710127",
            "bits_per_raw_sample": "8",
            "nb_frames": "1636",
            "disposition": {
                "default": 1,
                "dub": 0,
                "original": 0,
                "comment": 0,
                "lyrics": 0,
                "karaoke": 0,
                "forced": 0,
                "hearing_impaired": 0,
                "visual_impaired": 0,
                "clean_effects": 0,
                "attached_pic": 0
            },
            "tags": {
                "rotate": "90",
                "creation_time": "2015-11-08 14:36:49",
                "language": "und",
                "handler_name": "Core Media Video"
            }
        }
    ],
    "format": {
        "nb_streams": 2,
        "nb_programs": 0,
        "format_name": "mov,mp4,m4a,3gp,3g2,mj2",
        "format_long_name": "QuickTime / MOV",
        "start_time": "0.000000",
        "duration": "54.563333",
        "size": "5488167",
        "bit_rate": "804667",
        "probe_score": 100,
        "tags": {
            "major_brand": "mp42",
            "minor_version": "1",
            "compatible_brands": "mp41mp42isom",
            "creation_time": "2015-11-08 14:36:49"
        }
    }
}</code>

你需要使用七牛的转码方式将 rotate 参数为 0
文档视频转码

1.安装ffmpeg
2.ffmpeg -i INPUT.AVI -vcodec libx264 -preset slower -crf 18 -threads 4 -vf transpose=2 -acodec copy OUTPUT.MKV

---

-i 待转码文件
-vcodec 选择视频编码。做过一番搜索，相比与MPEG2, MPEG4等，H.264是公认最好的高清编码格式，同时压缩率也高于MPEG4，所以我选择使用H.264(libx264)进行视频编码。

-preset 选择编码预设，更慢=更好的视频质量，可选取值为 ultrafast,superfast, veryfast, faster, fast, medium, slow, slower, veryslow, placebo。placebo是没用的取值。

-crf Constant Rate Factor，0~51之间取值，0为无损，23为默认取值，取值越大，视频整体质量越差。一般建议在18～28之间取值。18已经达到视觉无损的效果，即人眼几乎察觉不到和原片的差别。

-threads 编码使用线程数，CPU几个核心就设置几个线程好了。

-vf 滤镜，我们只需要用到旋转滤镜transpose=2，transpose滤镜可取0-3，0为逆时针90°且垂直翻转，1为顺时针旋转90°，2为逆时针旋转90°，3为顺时针90°且垂直翻转。

-acodec 音频编码，这里直接设置为copy保留原文件音频编码。

最后设置输出文件为OUTPUT.MKV