| Bind the C libraries a call actually needs 87e5be9 nandi 9d ago | 1 | /* A flat C face for openh264's encoder. |
| 2 | * |
| 3 | * WHY THIS EXISTS. openh264's C API is not flat. `ISVCEncoder` is |
| 4 | * `const ISVCEncoderVtbl*` — a pointer to a table of function pointers — so |
| 5 | * calling Initialize or EncodeFrame means dereferencing the object, reading a |
| 6 | * slot, and calling through it. jolt.ffi cannot do that: Chez fixes a foreign |
| 7 | * procedure's types when it COMPILES it, and the target has to be a literal C |
| 8 | * symbol name rather than a function pointer (see jolt/ffi.clj, "the target |
| 9 | * must be a literal C symbol name"). So the vtable is walked here, in C, and |
| 10 | * what jolt binds is the five plain symbols below. |
| 11 | * |
| 12 | * It is deliberately thin. No policy, no buffering beyond what openh264's own |
| 13 | * output demands, and no decisions that belong in frq — the shim exists to |
| 14 | * change a calling convention, not to be a video pipeline. |
| 15 | * |
| 16 | * THE ONE THING IT DOES DO is flatten the output. openh264 hands back an |
| 17 | * SFrameBSInfo describing up to MAX_LAYER_NUM_OF_FRAME layers, each with its |
| 18 | * own NAL count and a shared bitstream buffer. A caller wanting one Annex B |
| 19 | * frame has to walk that; doing it in jolt would mean reading nested C structs |
| 20 | * whose layout is openh264's business. It is copied into one contiguous |
| 21 | * buffer owned by the encoder handle and handed over as a borrowed span, |
| 22 | * valid until the next encode — which is exactly the contract frq.av already |
| 23 | * has for a video frame. |
| 24 | */ |
| 25 | #include <stdlib.h> |
| 26 | #include <string.h> |
| 27 | #include <stdint.h> |
| 28 | #include <wels/codec_api.h> |
| 29 | #include <wels/codec_app_def.h> |
| 30 | |
| 31 | typedef struct { |
| 32 | ISVCEncoder *enc; |
| 33 | unsigned char *out; /* flattened Annex B, grown as needed */ |
| 34 | size_t out_cap; |
| 35 | int width, height; |
| 36 | } frq_h264; |
| 37 | |
| 38 | /* Answers 0 on success, or openh264's own non-zero return. */ |
| 39 | int frq_h264_open(int width, int height, int fps, int bitrate, void **handle) { |
| 40 | ISVCEncoder *enc = NULL; |
| 41 | frq_h264 *h; |
| 42 | SEncParamBase p; |
| 43 | int rc; |
| 44 | |
| 45 | *handle = NULL; |
| 46 | rc = WelsCreateSVCEncoder(&enc); |
| 47 | if (rc != 0 || enc == NULL) return rc ? rc : -1; |
| 48 | |
| 49 | memset(&p, 0, sizeof(p)); |
| 50 | p.iUsageType = CAMERA_VIDEO_REAL_TIME; |
| 51 | p.iPicWidth = width; |
| 52 | p.iPicHeight = height; |
| 53 | p.iTargetBitrate = bitrate; |
| 54 | p.fMaxFrameRate = (float)fps; |
| 55 | |
| 56 | rc = (*enc)->Initialize(enc, &p); |
| 57 | if (rc != 0) { WelsDestroySVCEncoder(enc); return rc; } |
| 58 | |
| 59 | h = (frq_h264 *)calloc(1, sizeof(frq_h264)); |
| 60 | if (h == NULL) { (*enc)->Uninitialize(enc); WelsDestroySVCEncoder(enc); return -1; } |
| 61 | h->enc = enc; h->width = width; h->height = height; |
| 62 | *handle = h; |
| 63 | return 0; |
| 64 | } |
| 65 | |
| 66 | /* Encode one I420 frame. |
| 67 | * |
| 68 | * `i420` is width*height luma followed by two (width/2)*(height/2) planes. |
| 69 | * On success answers 0 and sets *out / *out_len to a BORROWED span, valid |
| 70 | * until the next call on this handle. *keyframe says whether it is an IDR. |
| 71 | * A frame openh264 chose to skip answers 0 with *out_len == 0. */ |
| 72 | int frq_h264_encode(void *handle, const unsigned char *i420, long long pts_us, |
| 73 | const unsigned char **out, int *out_len, int *keyframe) { |
| 74 | frq_h264 *h = (frq_h264 *)handle; |
| 75 | SSourcePicture pic; |
| 76 | SFrameBSInfo info; |
| 77 | int rc, i, j, total = 0, off = 0; |
| 78 | |
| 79 | *out = NULL; *out_len = 0; *keyframe = 0; |
| 80 | |
| 81 | memset(&pic, 0, sizeof(pic)); |
| 82 | pic.iPicWidth = h->width; |
| 83 | pic.iPicHeight = h->height; |
| 84 | pic.iColorFormat = videoFormatI420; |
| 85 | pic.iStride[0] = h->width; |
| 86 | pic.iStride[1] = h->width / 2; |
| 87 | pic.iStride[2] = h->width / 2; |
| 88 | pic.pData[0] = (unsigned char *)i420; |
| 89 | pic.pData[1] = pic.pData[0] + h->width * h->height; |
| 90 | pic.pData[2] = pic.pData[1] + (h->width / 2) * (h->height / 2); |
| 91 | pic.uiTimeStamp = pts_us / 1000; /* openh264 counts milliseconds */ |
| 92 | |
| 93 | memset(&info, 0, sizeof(info)); |
| 94 | rc = (*h->enc)->EncodeFrame(h->enc, &pic, &info); |
| 95 | if (rc != cmResultSuccess) return rc; |
| 96 | if (info.eFrameType == videoFrameTypeSkip) return 0; |
| 97 | |
| 98 | for (i = 0; i < info.iLayerNum; i++) |
| 99 | for (j = 0; j < info.sLayerInfo[i].iNalCount; j++) |
| 100 | total += info.sLayerInfo[i].pNalLengthInByte[j]; |
| 101 | |
| 102 | if ((size_t)total > h->out_cap) { |
| 103 | unsigned char *grown = (unsigned char *)realloc(h->out, (size_t)total); |
| 104 | if (grown == NULL) return -1; |
| 105 | h->out = grown; h->out_cap = (size_t)total; |
| 106 | } |
| 107 | for (i = 0; i < info.iLayerNum; i++) { |
| 108 | int n = 0, k; |
| 109 | for (k = 0; k < info.sLayerInfo[i].iNalCount; k++) |
| 110 | n += info.sLayerInfo[i].pNalLengthInByte[k]; |
| 111 | memcpy(h->out + off, info.sLayerInfo[i].pBsBuf, (size_t)n); |
| 112 | off += n; |
| 113 | } |
| 114 | |
| 115 | *out = h->out; |
| 116 | *out_len = total; |
| 117 | *keyframe = (info.eFrameType == videoFrameTypeIDR); |
| 118 | return 0; |
| 119 | } |
| 120 | |
| 121 | int frq_h264_force_keyframe(void *handle) { |
| 122 | frq_h264 *h = (frq_h264 *)handle; |
| 123 | return (*h->enc)->ForceIntraFrame(h->enc, true); |
| 124 | } |
| 125 | |
| 126 | void frq_h264_close(void *handle) { |
| 127 | frq_h264 *h = (frq_h264 *)handle; |
| 128 | if (h == NULL) return; |
| 129 | if (h->enc) { (*h->enc)->Uninitialize(h->enc); WelsDestroySVCEncoder(h->enc); } |
| 130 | free(h->out); |
| 131 | free(h); |
| 132 | } |