Large timestamp gap detected; may cause AV sync to drift check and aac frame generate code.

flv-demuxer.ts

        // AAC raw frame data
        let dts = this._timestampBase + ts;

        // check large timestamp gap caused av drift
        if (this._expectTsAudio === -1) {
          this._expectTsAudio = dts; // set base ts
        }

        let generated = false;
        const delta = dts - this._expectTsAudio;

        if (delta > this._driftThreshold) {
          logger.warn(`Large timestamp gap detected; may cause AV sync to drift. time: ${dts} expected: ${this._expectTsAudio} delta: ${delta}`);

          if (Config.enableFillAACGap) {
            // 已生成空帧填补空隙，_driftThreshold不用变化
            // this._driftThreshold = delta;
            // generate aac frame
            const from = Math.round(this._expectTsAudio);
            const to = dts;
            const refSampleDuration = Math.round(meta.refSampleDuration);
            const len = Math.round(delta / refSampleDuration) - 1;

            dts = from;
            const aacSample = { unit: aacData.data, dts: dts, pts: dts, cts: 0 };
            track.samples.push(aacSample);
            track.length += aacData.data.length;

            for (let i = 0; i < len; i++) {
              const data = AAC.getSilentFrame(meta.codec, meta.channelCount);
              dts += refSampleDuration;
              if (i === len - 1) {
                dts = to;
              }
              const aac = { unit: data, dts: dts, pts: dts, cts: 0 }
              track.samples.push(aac);
              track.length += data.length;
            }
            this._expectTsAudio = to;

            generated = true;
            logger.warn(`generated ${len} frames.`);
          } else {
            this._driftThreshold = delta;
          }
        }

        if (!generated) {
          const aacSample = { unit: aacData.data, dts: dts, pts: dts, cts: 0 };
          track.samples.push(aacSample);
          track.length += aacData.data.length;
        }

        this._expectTsAudio += meta.refSampleDuration;