付费二次开发 ffmpeg，将 dash 流中的 data:image/png;base64 格式的字幕，压缩进视频。

需求：
修改 ffmpeg dash 模块，识别 dash 流中的 base64 格式的 png 字幕，将其压缩到视频内部。
预算：5K-10K

有没有大佬接啊？
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媒体详细信息如下：

Stream #0:4: Video: h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1280x720 [SAR 1:1 DAR 16:9], 25 fps, 25 tbr, 90k tbn, 50 tbc (default)
Metadata:
variant_bitrate : 1500000
id : 162/video-cif-stream-5
Stream #0:5(kor): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp (default)
Metadata:
variant_bitrate : 1024000
id : 80/video-cif-stream-1
Stream #0:6(may): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp (default)
Metadata:
variant_bitrate : 1024000
id : 82/video-cif-stream-1
Stream #0:7(chi): Audio: aac (HE-AAC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp (default)
Metadata:
variant_bitrate : 1024000
id : 83/video-cif-stream-1
Stream #0:8(may): Data: none (stpp / 0x70707473) (default)
Metadata:
id : subtitle/smptett_frag_bitmap_may_profile_0_video-cif-stream-1
Stream #0:9(chi): Data: none (stpp / 0x70707473) (default)
Metadata:
id : subtitle/smptett_frag_bitmap_chi_profile_0_video-cif-stream-1
Stream #0:10(eng): Data: none (stpp / 0x70707473) (default)
Metadata:
id : subtitle/smptett_frag_bitmap_eng_profile_0_video-cif-stream-1

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字幕是 base64 格式的 png 图片

data:image/png;base64,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